Silicon is the material most commonly used in the manufacturing of photovoltaic (PV) cells. In the current study, laboratory experiments of purification of solar cell silicon materials through filtration are carried o...Silicon is the material most commonly used in the manufacturing of photovoltaic (PV) cells. In the current study, laboratory experiments of purification of solar cell silicon materials through filtration are carried out. Inclusion removal from silicon was investigated. The purpose is to achieve clean silicon materials for solar cells. Silicon samples and filter samples were analyzed using microscope observation, EPMA, and X-ray detection. Silicon nitride (Si3N4) and silicon carbide (SiC) particles are the main non-metallic inclusions present in top-cut silicon scrap. Almost all inclusions larger than 10 μm can be removed from silicon by the porous foam filter. In mass fraction, more than 90% inclusions are removed. Si3N4 particles are mainly removed on the top surface of the filter, and SiC particles are mainly removed by entering the pores and attaching to the filter material. SiC inclusions are not only simply attached on the surface of the filter material, but are found also inside the filter material. There are SiC bridges near the filter materials. These bridges may fill the spaces between filter material, and this will further retard inclusions passing through the filter. Three-dimensional turbulent fluid flow and inclusion motion in the filter was calculated. Both experimental observation and fluid flow simulation indicate that most of the inclusions are entrapped at the upper part of the filter.展开更多
The monocrystalline silicon is a promising material that could be used in solar cells that convert light into electricity. Although the cost of ordinary silicon (Si) solar cells has decreased significantly over the pa...The monocrystalline silicon is a promising material that could be used in solar cells that convert light into electricity. Although the cost of ordinary silicon (Si) solar cells has decreased significantly over the past two decades, the conversion efficiency of these cells has remained relatively high. While solar cells have a great potential as a device of renewable energy, the high cost they incur per Watt continues to be a significant barrier to their widespread implementation. As a consequence, it is vital to conduct research into alternate materials that may be used in the construction of solar cells. The heterojunction solar cell (HJSC), which is based on n-type zinc oxide (n-ZnO) and p-type silicon (p-Si), is one of the numerous alternatives of the typical Si single homojunction solar cell. There are many deficiencies that can be found in the published research on n-ZnO/p-Si heterojunction solar cell. Inconsistencies in the stated value of open circuit voltage (V<sub>oc</sub>) of the solar cell are one example of deficiency. The absence of a full theoretical study to evaluate the potential of the solar cell structure is another deficiency that can be found in these researches. A lower value of experimentally obtained V<sub>OC</sub> in comparison to the theoretical prediction based on the band-gap between n-ZnO and p-Si. There needs to be more consensus among scientists regarding the optimal conditions for the growth of zinc oxide. Many software’s are available for simulating and optimizing the solar cells based on these parameters. For this purpose, in this dissertation, I provide computational results relevant to n-ZnO/p-Si HJSC to overcome deficiencies that have been identified. While modeling and simulating the potential of the solar cell structure with AFORS-HET, it is essential to consider the constraints that exist in the real world. AFORS-HET was explicitly designed to mimic the multilayer solar cell arrangement. In AFORS-HET, we can add up to seven layers for solar cell layout. By using this software, we can figure out the open circuit voltage (V<sub>OC</sub>), the short circuit current (J<sub>SC</sub>), the quantum efficiency (QE, %), the heterojunction energy band structure, and the power conversion efficiency (PCE).展开更多
Silicon passivated emitter and rear contact(PERC) solar cells with V-groove texture were fabricated using maskless alkaline solution etching with in-house developed additive. Compared with the traditional pyramid text...Silicon passivated emitter and rear contact(PERC) solar cells with V-groove texture were fabricated using maskless alkaline solution etching with in-house developed additive. Compared with the traditional pyramid texture, the V-groove texture possesses superior effective minority carrier lifetime, enhanced p–n junction quality and better applied filling factor(FF). In addition, a V-groove texture can greatly reduce the shading area and edge damage of front Ag electrodes when the V-groove direction is parallel to the gridline electrodes. Due to these factors, the V-groove solar cells have a higher efficiency(21.78%) than pyramid solar cells(21.62%). Interestingly, external quantum efficiency(EQE) and reflectance of the V-groove solar cells exhibit a slight decrease when the incident light angle(θ) is increased from 0° to 75°, which confirms the excellent quasi omnidirectionality of the V-groove solar cells. The proposed V-groove solar cell design shows a 2.84% relative enhancement of energy output over traditional pyramid solar cells.展开更多
The ultraviolet(UV)light stability of silicon heterojunction(SHJ)solar cells should be addressed before large-scale production and applications.Introducing downshifting(DS)nanophosphors on top of solar cells that can ...The ultraviolet(UV)light stability of silicon heterojunction(SHJ)solar cells should be addressed before large-scale production and applications.Introducing downshifting(DS)nanophosphors on top of solar cells that can convert UV light to visible light may reduce UV-induced degradation(UVID)without sacrificing the power conversion efficiency(PCE).Herein,a novel composite DS nanomaterial composed of YVO_(4):Eu^(3+),Bi^(3+)nanoparticles(NPs)and AgNPs was synthesized and introduced onto the incident light side of industrial SHJ solar cells to achieve UV shielding.The YVO_(4):Eu^(3+),Bi^(3+)NPs and Ag NPs were synthesized via a sol-gel method and a wet chemical reduction method,respectively.Then,a composite structure of the YVO_(4):Eu^(3+),Bi^(3+)NPs decorated with Ag NPs was synthesized by an ultrasonic method.The emission intensities of the YVO_(4):Eu^(3+),Bi^(3+)nanophosphors were significantly enhanced upon decoration with an appropriate amount of~20 nm Ag NPs due to the localized surface plasmon resonance(LSPR)effect.Upon the introduction of LSPR-enhanced downshifting,the SHJ solar cells exhibited an~0.54%relative decrease in PCE degradation under UV irradiation with a cumulative dose of 45 k W h compared to their counterparts,suggesting excellent potential for application in UV-light stability enhancement of solar cells or modules.展开更多
The bifacial silicon solar cell subjected to a magnetic field, is illuminated by the back side by a monochromatic light in frequency modulation, with high absorption, At minority carriers diffusion coefficient resonan...The bifacial silicon solar cell subjected to a magnetic field, is illuminated by the back side by a monochromatic light in frequency modulation, with high absorption, At minority carriers diffusion coefficient resonance frequency, a graphical study of the expressions of recombination velocity on the rear side is carried out. The optimum thickness of the base of the bifacial solar cell is deduced for each resonance frequency.展开更多
In this work,we developed a simple and direct circuit model with a dual two-diode model that can be solved by a SPICE numerical simulation to comprehensively describe the monolithic perovskite/crystalline silicon(PVS/...In this work,we developed a simple and direct circuit model with a dual two-diode model that can be solved by a SPICE numerical simulation to comprehensively describe the monolithic perovskite/crystalline silicon(PVS/c-Si)tandem solar cells.We are able to reveal the effects of different efficiency-loss mechanisms based on the illuminated current density-voltage(J-V),semi-log dark J-V,and local ideality factor(m-V)curves.The effects of the individual efficiency-loss mechanism on the tandem cell’s efficiency are discussed,including the exp(V/VT)and exp(V/2VT)recombination,the whole cell’s and subcell’s shunts,and the Ohmic-contact or Schottky-contact of the intermediate junction.We can also fit a practical J-V curve and find a specific group of parameters by the trial-and-error method.Although the fitted parameters are not a unique solution,they are valuable clues for identifying the efficiency loss with the aid of the cell’s structure and experimental processes.This method can also serve as an open platform for analyzing other tandem solar cells by substituting the corresponding circuit models.In summary,we developed a simple and effective methodology to diagnose the efficiency-loss source of a monolithic PVS/c-Si tandem cell,which is helpful to researchers who wish to adopt the proper approaches to improve their solar cells.展开更多
The bifacial silicon solar cell, placed at temperature (T) and illuminated from the back side by monochromatic light in frequency modulation (ω), is studied from the frequency dynamic diffusion equation, relative to ...The bifacial silicon solar cell, placed at temperature (T) and illuminated from the back side by monochromatic light in frequency modulation (ω), is studied from the frequency dynamic diffusion equation, relative to the density of excess minority carriers in the base. The expressions of the dynamic recombination velocities of the minority carriers on the rear side of the base Sb1(D(ω, T);H) and Sb2(α, D(ω, T);H), are analyzed as a function of the dynamic diffusion coefficient (D(ω, T)), the absorption coefficient (α(λ)) and the thickness of the base (H). Thus their graphic representation makes it possible to go up, to the base optimum thickness (Hopt(ω, T)), for different temperature values and frequency ranges of modulation of monochromatic light, of strong penetration. The base optimum thickness (Hopt(ω, T)) decreases with temperature, regardless of the frequency range and allows the realization of the solar cell with few material (Si).展开更多
The effects of surface texturing on spherical silicon solar cells were investigated. Surface texturing for spherical Si solar cells was prepared by immersing p-type spherical Si crystals in KOH solution with stirring....The effects of surface texturing on spherical silicon solar cells were investigated. Surface texturing for spherical Si solar cells was prepared by immersing p-type spherical Si crystals in KOH solution with stirring. Two kinds of texture feature sizes (1 and 5 μm pyramids) were prepared by changing stirring speed. After fabrication through our baseline processes, these cells were evaluated by solar cell performance and external quantum efficiency. The cell with 1 and 5 μm pyramids shows the short circuit current density (Jsc) value of 31.9 and 33.2 mA·cm-2, which is 9% and 13% relative increase compared to the cell without texturing. Furthermore, the cell with 5 μm pyramids has a higher open-circuit voltage (0.589 V) than the cell with 1 μm pyramids (0.577 V). As a result, the conversion efficiency was improved from 11.4% for the cell without texturing to 12.1% for the cell with 5 μm pyramids.展开更多
Polycrystalline Si(poly-Si)-based passivating contacts are promising candidates for high-efficiency crystalline Si solar cells.We show that nanosecond-scale pulsed laser melting(PLM)is an industrially viable technique...Polycrystalline Si(poly-Si)-based passivating contacts are promising candidates for high-efficiency crystalline Si solar cells.We show that nanosecond-scale pulsed laser melting(PLM)is an industrially viable technique to fabricate such contacts with precisely controlled dopant concentration profiles that exceed the solid solubility limit.We demonstrate that conventionally doped,hole-selective poly-Si/SiO_(x)contacts that provide poor surface passivation of c-Si can be replaced with Ga-or B-doped contacts based on non-equilibrium doping.We overcome the solid solubility limit for both dopants in poly-Si by rapid cooling and recrystallization over a timescale of∼25 ns.We show an active Ga dopant concentration of∼3×10^(20)cm^(−3)in poly-Si which is six times higher than its solubility limit in c-Si,and a B dopant concentration as high as∼10^(21) cm^(−3).We measure an implied open-circuit voltage of 735 mV for Ga-doped poly-Si/SiO_(x)contacts on Czochralski Si with a low contact resistivity of 35.5±2.4 mΩcm^(2).Scanning spreading resistance microscopy and Kelvin probe force microscopy show large diffusion and drift current in the p-n junction that contributes to the low contact resistivity.Our results suggest that PLM can be extended for hyperdoping of other semiconductors with low solubility atoms to enable high-efficiency devices.展开更多
Mono-crystalline silicon solar cells with a passivated emitter rear contact(PERC)configuration have attracted extensive attention from both industry and scientific communities.A record efficiency of 24.06%on p-type si...Mono-crystalline silicon solar cells with a passivated emitter rear contact(PERC)configuration have attracted extensive attention from both industry and scientific communities.A record efficiency of 24.06%on p-type silicon wafer and mass production efficiency around 22%have been demonstrated,mainly due to its superior rear side passivation.In this work,the PERC solar cells with a p-type silicon wafer were numerically studied in terms of the surface passivation,quality of silicon wafer and metal electrodes.A rational way to achieve a 24%mass-production efficiency was proposed.Free energy loss analyses were adopted to address the loss sources with respect to the limit efficiency of 29%,which provides a guideline for the design and manufacture of a high-efficiency PERC solar cell.展开更多
In order to enhance the p-type doping concentration in the LBSF, boron was added into the aluminum paste and boron doped local back surface field(B-LBSF) was successfully fabricated in this work. Through boron doping ...In order to enhance the p-type doping concentration in the LBSF, boron was added into the aluminum paste and boron doped local back surface field(B-LBSF) was successfully fabricated in this work. Through boron doping in the LBSF, much higher doping concentration was observed for the B-LBSF over the Al-LBSF. Higher doping concentration in the LBSF is expected to lead to better rear passivation and lower rear contact resistance. Based on one thousand pieces of solar cells for each type, it was found that the rear passivated crystalline silicon solar cells with B-LBSF showed statistical improvement in their photovoltaic properties over those with Al-LBSF.展开更多
The aim of this work is to present a theoretical study of external magnetic field effect on a bifacial silicon solar cell’s electrical parameters (peak power, fill factor and load resistance) using the J-V and P-V ch...The aim of this work is to present a theoretical study of external magnetic field effect on a bifacial silicon solar cell’s electrical parameters (peak power, fill factor and load resistance) using the J-V and P-V characteristics. After the resolution of the magneto transport equation and continuity equation of excess minority carriers in the base of the bifacial silicon solar cell under multispectral illumination, the photo-current density and the photovoltage are determined and the J-V and P-V curves are plotted. Using simultaneously the J-V and P-V curves, we determine, according to magnetic field intensity, the peak photocurrent density, the peak photovoltage, the peak electric power, the fill factor and the load resistance at the peak power point. The numerical data show that the solar cell’s peak power decreases with magnetic field intensity while the fill factor and the load resistance increase.展开更多
A space monocrystalline silicon(c-Si) solar cell under low-energy(< 1 MeV) electron irradiation was investigated using noncontact photocarrier radiometry(PCR). Monte Carlo simulation(MCS) was employed to characteri...A space monocrystalline silicon(c-Si) solar cell under low-energy(< 1 MeV) electron irradiation was investigated using noncontact photocarrier radiometry(PCR). Monte Carlo simulation(MCS) was employed to characterize the effect of different energy electron irradiation on the c-Si solar cell. The carrier transport parameters(carrier lifetime, diffusion coefficient, and surface recombination velocities) were obtained by best fitting the experimental results with a theoretical one-dimensional two-layer PCR model. The results showed that the increase of the irradiation electron energy caused a large reduction of the carrier lifetime and diffusion length. Furthermore, the rear surface recombination velocity of the Si:p base of the solar cell at the irradiation electron energy of 1 Me V was dramatically enhanced due to 1 MeV electron passing through the whole cell. Short-circuit current(I sc) degradation evaluated by PCR was in good agreement with that obtained by electrical measurement.展开更多
A novel structure of Ag grid/SiN_x/n^+-c-Si/n-c-Si/i-a-Si:H/p^+-a-Si:H/TCO/Ag grid was designed to increase the efficiency of bifacial amorphous/crystalline silicon-based solar cells and reduce the rear material consu...A novel structure of Ag grid/SiN_x/n^+-c-Si/n-c-Si/i-a-Si:H/p^+-a-Si:H/TCO/Ag grid was designed to increase the efficiency of bifacial amorphous/crystalline silicon-based solar cells and reduce the rear material consumption and production cost. The simulation results show that the new structure obtains higher efficiency compared with the typical bifacial amorphous/crystalline silicon-based solar cell because of an increase in the short-circuit current(J_(sc)), while retaining the advantages of a high open-circuit voltage, low temperature coefficient, and good weak-light performance. Moreover,real cells composed of the novel structure with dimensions of 75 mm × 75 mm were fabricated by a special fabrication recipe based on industrial processes. Without parameter optimization, the cell efficiency reached 21.1% with the J_(sc) of 41.7 mA/cm^2. In addition, the novel structure attained 28.55% potential conversion efficiency under an illumination of AM 1.5 G, 100 mW/cm^2. We conclude that the configuration of the Ag grid/SiN_x/n^+-c-Si/n-c-Si/i-a-Si:H/p^+-a-Si:H/TCO/Ag grid is a promising structure for high efficiency and low cost.展开更多
By inserting a thin highly doped crystalline silicon layer between the base region and amorphous silicon layer in an interdigitated back-contact(IBC) silicon solar cell, a new passivation layer is investigated. The pa...By inserting a thin highly doped crystalline silicon layer between the base region and amorphous silicon layer in an interdigitated back-contact(IBC) silicon solar cell, a new passivation layer is investigated. The passivation layer performance is characterized by numerical simulations. Moreover, the dependence of the output parameters of the solar cell on the additional layer parameters(doping concentration and thickness) is studied. By optimizing the additional passivation layer in terms of doping concentration and thickness, the power conversion efficiency could be improved by a factor of2.5%, open circuit voltage is increased by 30 mV and the fill factor of the solar cell by 7.4%. The performance enhancement is achieved due to the decrease of recombination rate, a decrease in solar cell resistivity and improvement of field effect passivation at heterojunction interface. The above-mentioned results are compared with reported results of the same conventional interdigitated back-contact silicon solar cell structure. Furthermore, the effect of a-Si:H/c-Si interface defect density on IBC silicon solar cell parameters with a new passivation layer is studied. The additional passivation layer also reduces the sensitivity of output parameter of solar cell to interface defect density.展开更多
This work deals with determining the optimum thickness of the base of an n<sup>+</sup>/p/p<sup>+</sup> silicon solar cell under monochromatic illumination in frequency modulation. The continuit...This work deals with determining the optimum thickness of the base of an n<sup>+</sup>/p/p<sup>+</sup> silicon solar cell under monochromatic illumination in frequency modulation. The continuity equation for the density of minority carriers generated in the base, by a monochromatic wavelength illumination (<i>λ</i>), with boundary conditions that impose recombination velocities (<i>Sf</i>) and (<i>Sb</i>) respectively at the junction and back surface, is resolved. The ac photocurrent is deduced and studied according to the recombination velocity at the junction, to extract the mathematical expressions of recombination velocity (<i>Sb</i>). By the graphic technique of comparing the two expressions obtained, depending on the thickness (<i>H</i>) of the base, for each frequency, the optimum thickness (Hopt) is obtained. It is then modeled according to the frequency, at the long wavelengths of the incident light. Thus, Hopt decreases due to the low relaxation time of minority carriers, when the frequency of modulation of incident light increases.展开更多
The monochromatic absorption coefficient of silicon, inducing the light penetration depth into the base of the solar cell, is used to determine the optimum thickness necessary for the production of a large photocurren...The monochromatic absorption coefficient of silicon, inducing the light penetration depth into the base of the solar cell, is used to determine the optimum thickness necessary for the production of a large photocurrent. The absorption-generation-diffusion and recombination (bulk and surface) phenomena are taken into account in the excess minority carrier continuity equation. The solution of this equation gives the photocurrent according to ab</span><span style="font-family:Verdana;">sorption and electronic parameters. Then from the obtained short circuit</span><span style="font-family:Verdana;"> photocurrent expression, excess minority carrier back surface recombination velocity is determined, function of the monochromatic absorption coefficient at a given wavelength. This latter plotted versus base thickness yields the optimum thickness of an n</span><sup><span style="font-family:Verdana;">+</span></sup><span style="font-family:Verdana;">-p-p</span><sup><span style="font-family:Verdana;">+</span></sup><span style="font-family:Verdana;"> solar cell, for each wavelength, which is in the range close to the energy band gap of the silicon material. This study provides a tool for improvement solar cell manufacture processes, through the mathematical relationship obtained from the thickness limit according to the absorption coefficient that allows base width optimization.展开更多
A bifacial silicon solar cell under monochromatic illumination in frequency modulation by the rear side is being studied for the optimization of base thickness. The density of photogenerated carriers in the base is ob...A bifacial silicon solar cell under monochromatic illumination in frequency modulation by the rear side is being studied for the optimization of base thickness. The density of photogenerated carriers in the base is obtained by resolution of the continuity equation, with the help of boundary conditions at the junction surface (n<sup><span style="font-family:Verdana;">+</span></sup><span style="font-family:Verdana;">/p) and the rear face (p/p</span><sup><span style="font-family:Verdana;">+</span></sup><span style="font-family:Verdana;">) of the base. For a short wavelength corresponding to a high absorption coefficient, the AC photocurrent density is calculated and represented according to the excess minority carrier’s recombination velocity at the junction, for different modulation frequency values. The expression of the AC recombination velocity of excess minority carriers at the rear surface of the base of the solar cell is then deduced, depending on both, the absorption coefficient of the silicon material and the thickness of the base. Compared to the intrinsic AC recombination velocity, the optimal thickness is extracted and modeled in a mathematical relationship, as a decreasing function of </span><span style="font-family:Verdana;">the </span><span style="font-family:Verdana;">modulated frequency of back illumination. Thus under these operating conditions</span><span style="font-family:Verdana;">,</span><span style="font-family:Verdana;"> a maximum short-circuit photocurrent is obtained and a low</span><span style="font-family:Verdana;">-</span><span style="font-family:Verdana;">cost bifacial solar cell can be achieved by reducing material (Si) to elaborate the base thickness.</span>展开更多
The modelling and determination of the geometric parameters of a solar cell are important data, which influence the evaluation of its performance under specific operating conditions, as well as its industrial developm...The modelling and determination of the geometric parameters of a solar cell are important data, which influence the evaluation of its performance under specific operating conditions, as well as its industrial development for a low cost. In this work, an n+/p/p+ crystalline silicon solar cell is studied under monochromatic illumination in modulation and placed in a constant magnetic field. The minority carriers’ diffusion coefficient (<em>D</em>(<em>ω</em>, <em>B</em>), in the (<em>p</em>) base leads to maximum values (Dmax) at resonance frequencies (<em>ωr</em>). These values are used in expressions of AC minority carriers recombination velocity (Sb(Dmax, H)) in the rear of the base, to extract the optimum thickness while solar cell is subjected to these specific conditions. Optimum thickness modelling relationships, depending respectively on Dmax, <em>ωr</em> and <em>B</em>, are then established, and will be data for industrial development of low-cost solar cells for specific use.展开更多
Base optimum thickness is determined for a front illuminated bifacial silicon solar cell n<sup>+</sup>-p<span style="font-size:10px;">-</span>p<sup>+</sup> under magnetic ...Base optimum thickness is determined for a front illuminated bifacial silicon solar cell n<sup>+</sup>-p<span style="font-size:10px;">-</span>p<sup>+</sup> under magnetic field. From the magneto transport equation relative to excess minority carriers in the base, with specific boundary conditions, the photocurrent is obtained. From this result the expressions of the carrier’s recombination velocity at the back surface are deducted. These new expressions of recombination velocity are plotted according to the depth of the base, to deduce the optimum thickness, which will allow the production, of a high short-circuit photocurrent. Calibration relationships of optimum thickness versus magnetic field were presented according to study ranges. It is found that, applied magnetic field imposes a weak thickness material for solar cell manufacturing leading to high short-circuit current.展开更多
文摘Silicon is the material most commonly used in the manufacturing of photovoltaic (PV) cells. In the current study, laboratory experiments of purification of solar cell silicon materials through filtration are carried out. Inclusion removal from silicon was investigated. The purpose is to achieve clean silicon materials for solar cells. Silicon samples and filter samples were analyzed using microscope observation, EPMA, and X-ray detection. Silicon nitride (Si3N4) and silicon carbide (SiC) particles are the main non-metallic inclusions present in top-cut silicon scrap. Almost all inclusions larger than 10 μm can be removed from silicon by the porous foam filter. In mass fraction, more than 90% inclusions are removed. Si3N4 particles are mainly removed on the top surface of the filter, and SiC particles are mainly removed by entering the pores and attaching to the filter material. SiC inclusions are not only simply attached on the surface of the filter material, but are found also inside the filter material. There are SiC bridges near the filter materials. These bridges may fill the spaces between filter material, and this will further retard inclusions passing through the filter. Three-dimensional turbulent fluid flow and inclusion motion in the filter was calculated. Both experimental observation and fluid flow simulation indicate that most of the inclusions are entrapped at the upper part of the filter.
文摘The monocrystalline silicon is a promising material that could be used in solar cells that convert light into electricity. Although the cost of ordinary silicon (Si) solar cells has decreased significantly over the past two decades, the conversion efficiency of these cells has remained relatively high. While solar cells have a great potential as a device of renewable energy, the high cost they incur per Watt continues to be a significant barrier to their widespread implementation. As a consequence, it is vital to conduct research into alternate materials that may be used in the construction of solar cells. The heterojunction solar cell (HJSC), which is based on n-type zinc oxide (n-ZnO) and p-type silicon (p-Si), is one of the numerous alternatives of the typical Si single homojunction solar cell. There are many deficiencies that can be found in the published research on n-ZnO/p-Si heterojunction solar cell. Inconsistencies in the stated value of open circuit voltage (V<sub>oc</sub>) of the solar cell are one example of deficiency. The absence of a full theoretical study to evaluate the potential of the solar cell structure is another deficiency that can be found in these researches. A lower value of experimentally obtained V<sub>OC</sub> in comparison to the theoretical prediction based on the band-gap between n-ZnO and p-Si. There needs to be more consensus among scientists regarding the optimal conditions for the growth of zinc oxide. Many software’s are available for simulating and optimizing the solar cells based on these parameters. For this purpose, in this dissertation, I provide computational results relevant to n-ZnO/p-Si HJSC to overcome deficiencies that have been identified. While modeling and simulating the potential of the solar cell structure with AFORS-HET, it is essential to consider the constraints that exist in the real world. AFORS-HET was explicitly designed to mimic the multilayer solar cell arrangement. In AFORS-HET, we can add up to seven layers for solar cell layout. By using this software, we can figure out the open circuit voltage (V<sub>OC</sub>), the short circuit current (J<sub>SC</sub>), the quantum efficiency (QE, %), the heterojunction energy band structure, and the power conversion efficiency (PCE).
基金Project supported by the Key-Area Research and Development Program of Guangdong Province,China (Grant No.2021B0101260001)Guangdong Basic and Applied Basic Research Foundation (Grant No.2019A1515110411)the National Natural Science Foundation of China (Grant No.61904201)。
文摘Silicon passivated emitter and rear contact(PERC) solar cells with V-groove texture were fabricated using maskless alkaline solution etching with in-house developed additive. Compared with the traditional pyramid texture, the V-groove texture possesses superior effective minority carrier lifetime, enhanced p–n junction quality and better applied filling factor(FF). In addition, a V-groove texture can greatly reduce the shading area and edge damage of front Ag electrodes when the V-groove direction is parallel to the gridline electrodes. Due to these factors, the V-groove solar cells have a higher efficiency(21.78%) than pyramid solar cells(21.62%). Interestingly, external quantum efficiency(EQE) and reflectance of the V-groove solar cells exhibit a slight decrease when the incident light angle(θ) is increased from 0° to 75°, which confirms the excellent quasi omnidirectionality of the V-groove solar cells. The proposed V-groove solar cell design shows a 2.84% relative enhancement of energy output over traditional pyramid solar cells.
基金supported by the National Natural Science Foundation of China (Grant Nos.52202276 and 51821002)the China Postdoctoral Science Foundation (Grant No.2022M712300)+1 种基金the Natural Science Foundation of the Jiangsu Higher Education Institutions of China (Grant No.22KJB480010)a project funded by the Priority Academic Program Development of Jiangsu Higher Education Institutions (PAPD)。
文摘The ultraviolet(UV)light stability of silicon heterojunction(SHJ)solar cells should be addressed before large-scale production and applications.Introducing downshifting(DS)nanophosphors on top of solar cells that can convert UV light to visible light may reduce UV-induced degradation(UVID)without sacrificing the power conversion efficiency(PCE).Herein,a novel composite DS nanomaterial composed of YVO_(4):Eu^(3+),Bi^(3+)nanoparticles(NPs)and AgNPs was synthesized and introduced onto the incident light side of industrial SHJ solar cells to achieve UV shielding.The YVO_(4):Eu^(3+),Bi^(3+)NPs and Ag NPs were synthesized via a sol-gel method and a wet chemical reduction method,respectively.Then,a composite structure of the YVO_(4):Eu^(3+),Bi^(3+)NPs decorated with Ag NPs was synthesized by an ultrasonic method.The emission intensities of the YVO_(4):Eu^(3+),Bi^(3+)nanophosphors were significantly enhanced upon decoration with an appropriate amount of~20 nm Ag NPs due to the localized surface plasmon resonance(LSPR)effect.Upon the introduction of LSPR-enhanced downshifting,the SHJ solar cells exhibited an~0.54%relative decrease in PCE degradation under UV irradiation with a cumulative dose of 45 k W h compared to their counterparts,suggesting excellent potential for application in UV-light stability enhancement of solar cells or modules.
文摘The bifacial silicon solar cell subjected to a magnetic field, is illuminated by the back side by a monochromatic light in frequency modulation, with high absorption, At minority carriers diffusion coefficient resonance frequency, a graphical study of the expressions of recombination velocity on the rear side is carried out. The optimum thickness of the base of the bifacial solar cell is deduced for each resonance frequency.
基金This work was supported by Zhejiang Energy Group(znkj-2018-118)Key Research and Development Program of Zhejiang Province(2021C01006)+5 种基金Key Project of Zhejiang Province(2021C04009)Science and technology projects in Liaoning Province 2021(2021JH1/10400104)Ningbo“Innovation 2025”Major Project(2020Z098)National Key R&D Program of China(2018YFB1500403)National Natural Science Foundation of China(61974178,61874177,62004199)Youth Innovation Promotion Association(2018333).
文摘In this work,we developed a simple and direct circuit model with a dual two-diode model that can be solved by a SPICE numerical simulation to comprehensively describe the monolithic perovskite/crystalline silicon(PVS/c-Si)tandem solar cells.We are able to reveal the effects of different efficiency-loss mechanisms based on the illuminated current density-voltage(J-V),semi-log dark J-V,and local ideality factor(m-V)curves.The effects of the individual efficiency-loss mechanism on the tandem cell’s efficiency are discussed,including the exp(V/VT)and exp(V/2VT)recombination,the whole cell’s and subcell’s shunts,and the Ohmic-contact or Schottky-contact of the intermediate junction.We can also fit a practical J-V curve and find a specific group of parameters by the trial-and-error method.Although the fitted parameters are not a unique solution,they are valuable clues for identifying the efficiency loss with the aid of the cell’s structure and experimental processes.This method can also serve as an open platform for analyzing other tandem solar cells by substituting the corresponding circuit models.In summary,we developed a simple and effective methodology to diagnose the efficiency-loss source of a monolithic PVS/c-Si tandem cell,which is helpful to researchers who wish to adopt the proper approaches to improve their solar cells.
文摘The bifacial silicon solar cell, placed at temperature (T) and illuminated from the back side by monochromatic light in frequency modulation (ω), is studied from the frequency dynamic diffusion equation, relative to the density of excess minority carriers in the base. The expressions of the dynamic recombination velocities of the minority carriers on the rear side of the base Sb1(D(ω, T);H) and Sb2(α, D(ω, T);H), are analyzed as a function of the dynamic diffusion coefficient (D(ω, T)), the absorption coefficient (α(λ)) and the thickness of the base (H). Thus their graphic representation makes it possible to go up, to the base optimum thickness (Hopt(ω, T)), for different temperature values and frequency ranges of modulation of monochromatic light, of strong penetration. The base optimum thickness (Hopt(ω, T)) decreases with temperature, regardless of the frequency range and allows the realization of the solar cell with few material (Si).
基金This work was partly financially supported by NEDO as an Investigation for Innovative PV Technology Project and Nisshin Electric Co., Ltd.
文摘The effects of surface texturing on spherical silicon solar cells were investigated. Surface texturing for spherical Si solar cells was prepared by immersing p-type spherical Si crystals in KOH solution with stirring. Two kinds of texture feature sizes (1 and 5 μm pyramids) were prepared by changing stirring speed. After fabrication through our baseline processes, these cells were evaluated by solar cell performance and external quantum efficiency. The cell with 1 and 5 μm pyramids shows the short circuit current density (Jsc) value of 31.9 and 33.2 mA·cm-2, which is 9% and 13% relative increase compared to the cell without texturing. Furthermore, the cell with 5 μm pyramids has a higher open-circuit voltage (0.589 V) than the cell with 1 μm pyramids (0.577 V). As a result, the conversion efficiency was improved from 11.4% for the cell without texturing to 12.1% for the cell with 5 μm pyramids.
基金the National Renewable Energy Laboratory,operated by Alliance for Sustainable Energy,LLC,for the U.S.Department of Energy(DOE)under Contract No.DE-AC36-08GO28308.
文摘Polycrystalline Si(poly-Si)-based passivating contacts are promising candidates for high-efficiency crystalline Si solar cells.We show that nanosecond-scale pulsed laser melting(PLM)is an industrially viable technique to fabricate such contacts with precisely controlled dopant concentration profiles that exceed the solid solubility limit.We demonstrate that conventionally doped,hole-selective poly-Si/SiO_(x)contacts that provide poor surface passivation of c-Si can be replaced with Ga-or B-doped contacts based on non-equilibrium doping.We overcome the solid solubility limit for both dopants in poly-Si by rapid cooling and recrystallization over a timescale of∼25 ns.We show an active Ga dopant concentration of∼3×10^(20)cm^(−3)in poly-Si which is six times higher than its solubility limit in c-Si,and a B dopant concentration as high as∼10^(21) cm^(−3).We measure an implied open-circuit voltage of 735 mV for Ga-doped poly-Si/SiO_(x)contacts on Czochralski Si with a low contact resistivity of 35.5±2.4 mΩcm^(2).Scanning spreading resistance microscopy and Kelvin probe force microscopy show large diffusion and drift current in the p-n junction that contributes to the low contact resistivity.Our results suggest that PLM can be extended for hyperdoping of other semiconductors with low solubility atoms to enable high-efficiency devices.
基金supported by the National Natural Science Foundation of China(No.61504155)。
文摘Mono-crystalline silicon solar cells with a passivated emitter rear contact(PERC)configuration have attracted extensive attention from both industry and scientific communities.A record efficiency of 24.06%on p-type silicon wafer and mass production efficiency around 22%have been demonstrated,mainly due to its superior rear side passivation.In this work,the PERC solar cells with a p-type silicon wafer were numerically studied in terms of the surface passivation,quality of silicon wafer and metal electrodes.A rational way to achieve a 24%mass-production efficiency was proposed.Free energy loss analyses were adopted to address the loss sources with respect to the limit efficiency of 29%,which provides a guideline for the design and manufacture of a high-efficiency PERC solar cell.
基金Funded by the National Natural Science Foundation of China(61366004)the Research Fund for the Doctoral Program of Higher Education(20123601110006)the Jiangxi Provincial Department of Education(KJLD13008)
文摘In order to enhance the p-type doping concentration in the LBSF, boron was added into the aluminum paste and boron doped local back surface field(B-LBSF) was successfully fabricated in this work. Through boron doping in the LBSF, much higher doping concentration was observed for the B-LBSF over the Al-LBSF. Higher doping concentration in the LBSF is expected to lead to better rear passivation and lower rear contact resistance. Based on one thousand pieces of solar cells for each type, it was found that the rear passivated crystalline silicon solar cells with B-LBSF showed statistical improvement in their photovoltaic properties over those with Al-LBSF.
文摘The aim of this work is to present a theoretical study of external magnetic field effect on a bifacial silicon solar cell’s electrical parameters (peak power, fill factor and load resistance) using the J-V and P-V characteristics. After the resolution of the magneto transport equation and continuity equation of excess minority carriers in the base of the bifacial silicon solar cell under multispectral illumination, the photo-current density and the photovoltage are determined and the J-V and P-V curves are plotted. Using simultaneously the J-V and P-V curves, we determine, according to magnetic field intensity, the peak photocurrent density, the peak photovoltage, the peak electric power, the fill factor and the load resistance at the peak power point. The numerical data show that the solar cell’s peak power decreases with magnetic field intensity while the fill factor and the load resistance increase.
文摘A space monocrystalline silicon(c-Si) solar cell under low-energy(< 1 MeV) electron irradiation was investigated using noncontact photocarrier radiometry(PCR). Monte Carlo simulation(MCS) was employed to characterize the effect of different energy electron irradiation on the c-Si solar cell. The carrier transport parameters(carrier lifetime, diffusion coefficient, and surface recombination velocities) were obtained by best fitting the experimental results with a theoretical one-dimensional two-layer PCR model. The results showed that the increase of the irradiation electron energy caused a large reduction of the carrier lifetime and diffusion length. Furthermore, the rear surface recombination velocity of the Si:p base of the solar cell at the irradiation electron energy of 1 Me V was dramatically enhanced due to 1 MeV electron passing through the whole cell. Short-circuit current(I sc) degradation evaluated by PCR was in good agreement with that obtained by electrical measurement.
基金Project supported by the Jiangxi Provincial Key Research and Development Foundation,China(Grant No.2016BBH80043)the Open Fund of Jiangsu Key Laboratory of Materials and Technology for Energy Conversion,China(Grant No.NJ20160032)the National Natural Science Foundation of China(Grant Nos.61741404,61464007,and 51561022)
文摘A novel structure of Ag grid/SiN_x/n^+-c-Si/n-c-Si/i-a-Si:H/p^+-a-Si:H/TCO/Ag grid was designed to increase the efficiency of bifacial amorphous/crystalline silicon-based solar cells and reduce the rear material consumption and production cost. The simulation results show that the new structure obtains higher efficiency compared with the typical bifacial amorphous/crystalline silicon-based solar cell because of an increase in the short-circuit current(J_(sc)), while retaining the advantages of a high open-circuit voltage, low temperature coefficient, and good weak-light performance. Moreover,real cells composed of the novel structure with dimensions of 75 mm × 75 mm were fabricated by a special fabrication recipe based on industrial processes. Without parameter optimization, the cell efficiency reached 21.1% with the J_(sc) of 41.7 mA/cm^2. In addition, the novel structure attained 28.55% potential conversion efficiency under an illumination of AM 1.5 G, 100 mW/cm^2. We conclude that the configuration of the Ag grid/SiN_x/n^+-c-Si/n-c-Si/i-a-Si:H/p^+-a-Si:H/TCO/Ag grid is a promising structure for high efficiency and low cost.
文摘By inserting a thin highly doped crystalline silicon layer between the base region and amorphous silicon layer in an interdigitated back-contact(IBC) silicon solar cell, a new passivation layer is investigated. The passivation layer performance is characterized by numerical simulations. Moreover, the dependence of the output parameters of the solar cell on the additional layer parameters(doping concentration and thickness) is studied. By optimizing the additional passivation layer in terms of doping concentration and thickness, the power conversion efficiency could be improved by a factor of2.5%, open circuit voltage is increased by 30 mV and the fill factor of the solar cell by 7.4%. The performance enhancement is achieved due to the decrease of recombination rate, a decrease in solar cell resistivity and improvement of field effect passivation at heterojunction interface. The above-mentioned results are compared with reported results of the same conventional interdigitated back-contact silicon solar cell structure. Furthermore, the effect of a-Si:H/c-Si interface defect density on IBC silicon solar cell parameters with a new passivation layer is studied. The additional passivation layer also reduces the sensitivity of output parameter of solar cell to interface defect density.
文摘This work deals with determining the optimum thickness of the base of an n<sup>+</sup>/p/p<sup>+</sup> silicon solar cell under monochromatic illumination in frequency modulation. The continuity equation for the density of minority carriers generated in the base, by a monochromatic wavelength illumination (<i>λ</i>), with boundary conditions that impose recombination velocities (<i>Sf</i>) and (<i>Sb</i>) respectively at the junction and back surface, is resolved. The ac photocurrent is deduced and studied according to the recombination velocity at the junction, to extract the mathematical expressions of recombination velocity (<i>Sb</i>). By the graphic technique of comparing the two expressions obtained, depending on the thickness (<i>H</i>) of the base, for each frequency, the optimum thickness (Hopt) is obtained. It is then modeled according to the frequency, at the long wavelengths of the incident light. Thus, Hopt decreases due to the low relaxation time of minority carriers, when the frequency of modulation of incident light increases.
文摘The monochromatic absorption coefficient of silicon, inducing the light penetration depth into the base of the solar cell, is used to determine the optimum thickness necessary for the production of a large photocurrent. The absorption-generation-diffusion and recombination (bulk and surface) phenomena are taken into account in the excess minority carrier continuity equation. The solution of this equation gives the photocurrent according to ab</span><span style="font-family:Verdana;">sorption and electronic parameters. Then from the obtained short circuit</span><span style="font-family:Verdana;"> photocurrent expression, excess minority carrier back surface recombination velocity is determined, function of the monochromatic absorption coefficient at a given wavelength. This latter plotted versus base thickness yields the optimum thickness of an n</span><sup><span style="font-family:Verdana;">+</span></sup><span style="font-family:Verdana;">-p-p</span><sup><span style="font-family:Verdana;">+</span></sup><span style="font-family:Verdana;"> solar cell, for each wavelength, which is in the range close to the energy band gap of the silicon material. This study provides a tool for improvement solar cell manufacture processes, through the mathematical relationship obtained from the thickness limit according to the absorption coefficient that allows base width optimization.
文摘A bifacial silicon solar cell under monochromatic illumination in frequency modulation by the rear side is being studied for the optimization of base thickness. The density of photogenerated carriers in the base is obtained by resolution of the continuity equation, with the help of boundary conditions at the junction surface (n<sup><span style="font-family:Verdana;">+</span></sup><span style="font-family:Verdana;">/p) and the rear face (p/p</span><sup><span style="font-family:Verdana;">+</span></sup><span style="font-family:Verdana;">) of the base. For a short wavelength corresponding to a high absorption coefficient, the AC photocurrent density is calculated and represented according to the excess minority carrier’s recombination velocity at the junction, for different modulation frequency values. The expression of the AC recombination velocity of excess minority carriers at the rear surface of the base of the solar cell is then deduced, depending on both, the absorption coefficient of the silicon material and the thickness of the base. Compared to the intrinsic AC recombination velocity, the optimal thickness is extracted and modeled in a mathematical relationship, as a decreasing function of </span><span style="font-family:Verdana;">the </span><span style="font-family:Verdana;">modulated frequency of back illumination. Thus under these operating conditions</span><span style="font-family:Verdana;">,</span><span style="font-family:Verdana;"> a maximum short-circuit photocurrent is obtained and a low</span><span style="font-family:Verdana;">-</span><span style="font-family:Verdana;">cost bifacial solar cell can be achieved by reducing material (Si) to elaborate the base thickness.</span>
文摘The modelling and determination of the geometric parameters of a solar cell are important data, which influence the evaluation of its performance under specific operating conditions, as well as its industrial development for a low cost. In this work, an n+/p/p+ crystalline silicon solar cell is studied under monochromatic illumination in modulation and placed in a constant magnetic field. The minority carriers’ diffusion coefficient (<em>D</em>(<em>ω</em>, <em>B</em>), in the (<em>p</em>) base leads to maximum values (Dmax) at resonance frequencies (<em>ωr</em>). These values are used in expressions of AC minority carriers recombination velocity (Sb(Dmax, H)) in the rear of the base, to extract the optimum thickness while solar cell is subjected to these specific conditions. Optimum thickness modelling relationships, depending respectively on Dmax, <em>ωr</em> and <em>B</em>, are then established, and will be data for industrial development of low-cost solar cells for specific use.
文摘Base optimum thickness is determined for a front illuminated bifacial silicon solar cell n<sup>+</sup>-p<span style="font-size:10px;">-</span>p<sup>+</sup> under magnetic field. From the magneto transport equation relative to excess minority carriers in the base, with specific boundary conditions, the photocurrent is obtained. From this result the expressions of the carrier’s recombination velocity at the back surface are deducted. These new expressions of recombination velocity are plotted according to the depth of the base, to deduce the optimum thickness, which will allow the production, of a high short-circuit photocurrent. Calibration relationships of optimum thickness versus magnetic field were presented according to study ranges. It is found that, applied magnetic field imposes a weak thickness material for solar cell manufacturing leading to high short-circuit current.
