Lithium-ion batteries(LIBs)and lithium-sulfur(Li–S)batteries are two types of energy storage systems with significance in both scientific research and commercialization.Nevertheless,the rational design of electrode m...Lithium-ion batteries(LIBs)and lithium-sulfur(Li–S)batteries are two types of energy storage systems with significance in both scientific research and commercialization.Nevertheless,the rational design of electrode materials for overcoming the bottlenecks of LIBs and Li–S batteries(such as low diffusion rates in LIBs and low sulfur utilization in Li–S batteries)remain the greatest challenge,while two-dimensional(2D)electrodes materials provide a solution because of their unique structural and electrochemical properties.In this article,from the perspective of ab-initio simulations,we review the design of 2D electrode materials for LIBs and Li–S batteries.We first propose the theoretical design principles for 2D electrodes,including stability,electronic properties,capacity,and ion diffusion descriptors.Next,classified examples of promising 2D electrodes designed by theoretical simulations are given,covering graphene,phosphorene,MXene,transition metal sulfides,and so on.Finally,common challenges and a future perspective are provided.This review paves the way for rational design of 2D electrode materials for LIBs and Li–S battery applications and may provide a guide for future experiments.展开更多
Energy conversion efficiency losses and limits of perovskite/silicon tandem solar cells are investigated by detailed balance calculations and photon management.An extended Shockley-Queisser model is used to identify f...Energy conversion efficiency losses and limits of perovskite/silicon tandem solar cells are investigated by detailed balance calculations and photon management.An extended Shockley-Queisser model is used to identify fundamental loss mechanisms and link the losses to the optics of solar cells.Photon management is used to minimize losses and maximize the energy conversion efficiency.The influence of photon management on the solar cell parameters of a perovskite single-junction solar cell and a perovskite/silicon solar cell is discussed in greater details.An optimized solar cell design of a perovskite/silicon tandem solar cell is presented,which allows for the realization of solar cells with energy conversion efficiencies exceeding 32%.展开更多
The photovoltaic performance of perovskite solar cells(PSCs)can be improved by utilizing efficient front contact.However,it has always been a significant challenge for fabricating high-quality,scalable,controllable,an...The photovoltaic performance of perovskite solar cells(PSCs)can be improved by utilizing efficient front contact.However,it has always been a significant challenge for fabricating high-quality,scalable,controllable,and cost-effective front contact.This study proposes a realistic multi-layer front contact design to realize efficient single-junction PSCs and perovskite/perovskite tandem solar cells(TSCs).As a critical part of the front contact,we prepared a highly compact titanium oxide(TiO2)film by industrially viable Spray Pyrolysis Deposition(SPD),which acts as a potential electron transport layer(ETL)for the fabrication of PSCs.Optimization and reproducibility of the TiO2 ETL were discreetly investigated while fabricating a set of planar PSCs.As the front contact has a significant influence on the optoelectronic properties of PSCs,hence,we investigated the optics and electrical effects of PSCs by three-dimensional(3D)finite-difference time-domain(FDTD)and finite element method(FEM)rigorous simulations.The investigation allows us to compare experimental results with the outcome from simulations.Furthermore,an optimized single-junction PSC is designed to enhance the energy conversion efficiency(ECE)by>30% compared to the planar reference PSC.Finally,the study has been progressed to the realization of all-perovskite TSC that can reach the ECE,exceeding 30%.Detailed guidance for the completion of high-performance PSCs is provided.展开更多
The research of ultraviolet photodetectors(UV PDs)have been attracting extensive attention,due to their important applications in many areas.In this study,PtSe2/GaN heterojunction is in-situ fabricated by synthesis of...The research of ultraviolet photodetectors(UV PDs)have been attracting extensive attention,due to their important applications in many areas.In this study,PtSe2/GaN heterojunction is in-situ fabricated by synthesis of large-area vertically standing two-dimensional(2D)PtSe2 film on n-GaN substrate.The PtSe2/GaN heterojunction device demonstrates excellent photoresponse properties under illumination by deep UV light of 265 nm at zero bias voltage.Further analysis reveals that a high responsivity of 193 mA·W^-1,an ultrahigh specific detectivity of 3.8 × 10^14 Jones,linear dynamic range of 155d B and current on/off ratio of^10^8,as well as fast response speeds of 45/102μs were obtained at zero bias voltage.Moreover,this device response quickly to the pulse laser of 266 nm with a rise time of 172 ns.Such high-performanee PtSe2/GaN heteroj u nction UV PD demonstrated in this work is far superior to previously reported results,suggesting that it has great potential for deep UV detection.展开更多
There is an emerging need for high-sensitivity solar-blind deep ultraviolet(DUV)photodetectors with an ultra-fast response speed.Although nanoscale devices based on Ga_(2)O_(3)nanostructures have been developed,their ...There is an emerging need for high-sensitivity solar-blind deep ultraviolet(DUV)photodetectors with an ultra-fast response speed.Although nanoscale devices based on Ga_(2)O_(3)nanostructures have been developed,their practical applications are greatly limited by their slow response speed as well as low specific detectivity.Here,the successful fabrication of two-/three-dimensional(2D/3D)graphene(Gr)/PtSe2/β-Ga_(2)O_(3)Schottky junction devices for high-sensitivity solar-blind DUV photodetectors is demonstrated.Benefitting from the high-quality 2D/3D Schottky junction,the vertically stacked structure,and the superior-quality transparent graphene electrode for effective carrier collection,the photodetector is highly sensitive to DUV light illumination and achieves a high responsivity of 76.2 mA/W,a large on/off current ratio of~105,along with an ultra-high ultraviolet(UV)/visible rejection ratio of 1.8×104.More importantly,it has an ultra-fast response time of 12µs and a remarkable specific detectivity of~1013 Jones.Finally,an excellent DUV imaging capability has been identified based on the Gr/PtSe2/β-Ga_(2)O_(3)Schottky junction photodetector,demonstrating its great potential application in DUV imaging systems.展开更多
The novel vertically standing Pt Se2 film on transparent quartz was prepared by selenization of platinum film deposited by the magnetron sputtering method, and an Nd:Lu VO4 passively mode-locked solid-state laser was ...The novel vertically standing Pt Se2 film on transparent quartz was prepared by selenization of platinum film deposited by the magnetron sputtering method, and an Nd:Lu VO4 passively mode-locked solid-state laser was realized by using the fabricated Pt Se2 film as a saturable absorber. The X-ray diffraction pattern and Raman spectrum of the film indicate its good crystallinity with a layered structure. The thickness of Pt Se2 film is measured to be 24 nm according to the cross-section height profile of the atomic force microscope image. Highresolution transmission electron microscopy images clearly demonstrate its vertically standing structure with an interlayer distance of 0.54 nm along the c-axis direction. The modulation depth(ΔT) and saturation fluence(Φs)of Pt Se2 film are measured to be 12.6% and 17.1 μJ∕cm2, respectively. The obtained mode-locked laser spectrum has a central wavelength of 1066.573 nm, with a 3 d B bandwidth of 0.106 nm. The transform limited pulse width of the mode-locked laser was calculated to be 15.8 ps. A maximum average output power of 180 m W with a working repetition rate of 61.3 MHz is obtained. To the best of our knowledge, this is the first report of the generation of ultrafast mode-locked laser pulses by using layered Pt Se2 as a saturable absorber.展开更多
Stable Q-switched and mode-locked erbium-doped fiber lasers(EDFLs)are first demonstrated by using the novel layered palladium disulfide(PdS2),a new member of group 10 transition metal dichalcogenides(TMDs)-based satur...Stable Q-switched and mode-locked erbium-doped fiber lasers(EDFLs)are first demonstrated by using the novel layered palladium disulfide(PdS2),a new member of group 10 transition metal dichalcogenides(TMDs)-based saturable absorbers(SAs).Self-started Q-switched operation at 1567 nm was achieved with a threshold pump power of 50.6 mW.The modulation ranges of pulse duration and repetition rate were characterized as 12.6-4.5μs and 17.2-26.0 kHz,respectively.Meanwhile,a mode-locked EDFL was also obtained with a pump power threshold of 106.4 mW.The achieved pulse duration is 803 fs,corresponding to a center wavelength of 1565.8 nm and4.48 nm 3 dB bandwidth.To the best of our knowledge,the achieved pulse duration of the mode-locked EDFL in this work is the narrowest compared with all other group 10 TMD SA-based lasers.展开更多
We report the design of a nanophotonic metaloxide front contact aimed at perovskite solar cells(PSCs)to enhance optoelectronic properties and device stability in the presence of ultraviolet(UV)light.High-quality Cr-do...We report the design of a nanophotonic metaloxide front contact aimed at perovskite solar cells(PSCs)to enhance optoelectronic properties and device stability in the presence of ultraviolet(UV)light.High-quality Cr-doped ZnO film was prepared by industrially feasible magnetron sputter deposition for the electron transport layer of PSCs.As a means,the influence of the Cr content on the film and device was systematically determined.In-depth device optics and electrical effects were studied using advanced three-dimensional opto-electrical multiphysics rigorous simulations,optimizing the front contact for realizing high performance.The numerical simulation was validated by fabricating PSCs optimized to reach high performance,energy conversion efficiency(ECE)=17.3%,open-circuit voltage(V_(OC))=1.08 V,short-circuit current density(J_(SC))=21.1 mA cm^(-2),and fillfactor(FF)=76%.Finally,a realistic front contact of nanophotonic architecture was proposed while improving broadband light absorption of the solar spectrum and light harvesting,resulting in enhanced quantum efficiency(QE).The nanophotonic PSC enables J_(SC)improvement by~17%while reducing the reflection by 12%,resulting in an estimated conversion efficiency over 23%.It is further demonstrated how the PSCs’UV-stability can be improved without considerably sacrificing optoelectronic performances.Particulars of nanophotonic designed ZnO:Cr front contact,PSCs device,and fabrication process are described.展开更多
基金supported by the Research Grants Council of the Hong Kong Special Administrative Region,China(PolyU152178/20 E)the Hong Kong Polytechnic University(1-W19S)Science and Technology Program of Guangdong Province of China(2020A0505090001).
文摘Lithium-ion batteries(LIBs)and lithium-sulfur(Li–S)batteries are two types of energy storage systems with significance in both scientific research and commercialization.Nevertheless,the rational design of electrode materials for overcoming the bottlenecks of LIBs and Li–S batteries(such as low diffusion rates in LIBs and low sulfur utilization in Li–S batteries)remain the greatest challenge,while two-dimensional(2D)electrodes materials provide a solution because of their unique structural and electrochemical properties.In this article,from the perspective of ab-initio simulations,we review the design of 2D electrode materials for LIBs and Li–S batteries.We first propose the theoretical design principles for 2D electrodes,including stability,electronic properties,capacity,and ion diffusion descriptors.Next,classified examples of promising 2D electrodes designed by theoretical simulations are given,covering graphene,phosphorene,MXene,transition metal sulfides,and so on.Finally,common challenges and a future perspective are provided.This review paves the way for rational design of 2D electrode materials for LIBs and Li–S battery applications and may provide a guide for future experiments.
基金financially supported by the Research Grants Council of Hong Kong,China(152093/18E)and the Hong Kong Polytechnic University(G-YBVG).
文摘Energy conversion efficiency losses and limits of perovskite/silicon tandem solar cells are investigated by detailed balance calculations and photon management.An extended Shockley-Queisser model is used to identify fundamental loss mechanisms and link the losses to the optics of solar cells.Photon management is used to minimize losses and maximize the energy conversion efficiency.The influence of photon management on the solar cell parameters of a perovskite single-junction solar cell and a perovskite/silicon solar cell is discussed in greater details.An optimized solar cell design of a perovskite/silicon tandem solar cell is presented,which allows for the realization of solar cells with energy conversion efficiencies exceeding 32%.
基金supported in part by the Research and Study Project of Tokai University General Research Organization and by the Grant-in-Aid for Scientific Research Grant Number 20H02838the Universiti Kebangsaan Malaysia for supporting this study through FRGS/1/2017/TK07/UKM/02/9 Grantsupported by the Research Grants Council of Hong Kong,China(Project Number:152093/18E).
文摘The photovoltaic performance of perovskite solar cells(PSCs)can be improved by utilizing efficient front contact.However,it has always been a significant challenge for fabricating high-quality,scalable,controllable,and cost-effective front contact.This study proposes a realistic multi-layer front contact design to realize efficient single-junction PSCs and perovskite/perovskite tandem solar cells(TSCs).As a critical part of the front contact,we prepared a highly compact titanium oxide(TiO2)film by industrially viable Spray Pyrolysis Deposition(SPD),which acts as a potential electron transport layer(ETL)for the fabrication of PSCs.Optimization and reproducibility of the TiO2 ETL were discreetly investigated while fabricating a set of planar PSCs.As the front contact has a significant influence on the optoelectronic properties of PSCs,hence,we investigated the optics and electrical effects of PSCs by three-dimensional(3D)finite-difference time-domain(FDTD)and finite element method(FEM)rigorous simulations.The investigation allows us to compare experimental results with the outcome from simulations.Furthermore,an optimized single-junction PSC is designed to enhance the energy conversion efficiency(ECE)by>30% compared to the planar reference PSC.Finally,the study has been progressed to the realization of all-perovskite TSC that can reach the ECE,exceeding 30%.Detailed guidance for the completion of high-performance PSCs is provided.
基金the National Natural Science Foundation of China(Nos.61605174 and 61774136)the Key Projects of Higher Education in Henan Province(No.17A140012)Research Grants Council,University Grants Committee(RGC,UGC)(GRF 152109/16E PolyU B-Q52T).
文摘The research of ultraviolet photodetectors(UV PDs)have been attracting extensive attention,due to their important applications in many areas.In this study,PtSe2/GaN heterojunction is in-situ fabricated by synthesis of large-area vertically standing two-dimensional(2D)PtSe2 film on n-GaN substrate.The PtSe2/GaN heterojunction device demonstrates excellent photoresponse properties under illumination by deep UV light of 265 nm at zero bias voltage.Further analysis reveals that a high responsivity of 193 mA·W^-1,an ultrahigh specific detectivity of 3.8 × 10^14 Jones,linear dynamic range of 155d B and current on/off ratio of^10^8,as well as fast response speeds of 45/102μs were obtained at zero bias voltage.Moreover,this device response quickly to the pulse laser of 266 nm with a rise time of 172 ns.Such high-performanee PtSe2/GaN heteroj u nction UV PD demonstrated in this work is far superior to previously reported results,suggesting that it has great potential for deep UV detection.
基金the National Natural Science Foundation of China(Nos.U2004165,51702017,and 11974016)the Natural Science Foundation of Henan Province,China(No.202300410376)Research Grants Council of Hong Kong,China(No.GRF 152093/18E PolyU B-Q65N).
文摘There is an emerging need for high-sensitivity solar-blind deep ultraviolet(DUV)photodetectors with an ultra-fast response speed.Although nanoscale devices based on Ga_(2)O_(3)nanostructures have been developed,their practical applications are greatly limited by their slow response speed as well as low specific detectivity.Here,the successful fabrication of two-/three-dimensional(2D/3D)graphene(Gr)/PtSe2/β-Ga_(2)O_(3)Schottky junction devices for high-sensitivity solar-blind DUV photodetectors is demonstrated.Benefitting from the high-quality 2D/3D Schottky junction,the vertically stacked structure,and the superior-quality transparent graphene electrode for effective carrier collection,the photodetector is highly sensitive to DUV light illumination and achieves a high responsivity of 76.2 mA/W,a large on/off current ratio of~105,along with an ultra-high ultraviolet(UV)/visible rejection ratio of 1.8×104.More importantly,it has an ultra-fast response time of 12µs and a remarkable specific detectivity of~1013 Jones.Finally,an excellent DUV imaging capability has been identified based on the Gr/PtSe2/β-Ga_(2)O_(3)Schottky junction photodetector,demonstrating its great potential application in DUV imaging systems.
基金National Natural Science Foundation of China(NSFC)(61705044)One-Hundred Young Talents Program of Guangdong University of Technology(GDUT)(220413145)+1 种基金Research Grants Council,University Grants Committee(RGC,UGC)(GRF 152109/16E Poly U B-Q52T)Hong Kong Polytechnic University(Poly U)(G-YBVG)
文摘The novel vertically standing Pt Se2 film on transparent quartz was prepared by selenization of platinum film deposited by the magnetron sputtering method, and an Nd:Lu VO4 passively mode-locked solid-state laser was realized by using the fabricated Pt Se2 film as a saturable absorber. The X-ray diffraction pattern and Raman spectrum of the film indicate its good crystallinity with a layered structure. The thickness of Pt Se2 film is measured to be 24 nm according to the cross-section height profile of the atomic force microscope image. Highresolution transmission electron microscopy images clearly demonstrate its vertically standing structure with an interlayer distance of 0.54 nm along the c-axis direction. The modulation depth(ΔT) and saturation fluence(Φs)of Pt Se2 film are measured to be 12.6% and 17.1 μJ∕cm2, respectively. The obtained mode-locked laser spectrum has a central wavelength of 1066.573 nm, with a 3 d B bandwidth of 0.106 nm. The transform limited pulse width of the mode-locked laser was calculated to be 15.8 ps. A maximum average output power of 180 m W with a working repetition rate of 61.3 MHz is obtained. To the best of our knowledge, this is the first report of the generation of ultrafast mode-locked laser pulses by using layered Pt Se2 as a saturable absorber.
基金Research Grants Council,University Grants Committee of Hong Kong,China(GRF 152109/16E Poly U B-Q52T)。
文摘Stable Q-switched and mode-locked erbium-doped fiber lasers(EDFLs)are first demonstrated by using the novel layered palladium disulfide(PdS2),a new member of group 10 transition metal dichalcogenides(TMDs)-based saturable absorbers(SAs).Self-started Q-switched operation at 1567 nm was achieved with a threshold pump power of 50.6 mW.The modulation ranges of pulse duration and repetition rate were characterized as 12.6-4.5μs and 17.2-26.0 kHz,respectively.Meanwhile,a mode-locked EDFL was also obtained with a pump power threshold of 106.4 mW.The achieved pulse duration is 803 fs,corresponding to a center wavelength of 1565.8 nm and4.48 nm 3 dB bandwidth.To the best of our knowledge,the achieved pulse duration of the mode-locked EDFL in this work is the narrowest compared with all other group 10 TMD SA-based lasers.
基金financial support through the Long-term Research Grant Scheme(LRGS/1/2019/UKM-UKM/6/1)their appreciation to Researchers Supporting Project number(RSP-2021/34),King Saud University,Riyadh,Saudi Arabiathe Innovation and Technology Commission of Hong Kong(Project No.GHP/040/19SZ)。
文摘We report the design of a nanophotonic metaloxide front contact aimed at perovskite solar cells(PSCs)to enhance optoelectronic properties and device stability in the presence of ultraviolet(UV)light.High-quality Cr-doped ZnO film was prepared by industrially feasible magnetron sputter deposition for the electron transport layer of PSCs.As a means,the influence of the Cr content on the film and device was systematically determined.In-depth device optics and electrical effects were studied using advanced three-dimensional opto-electrical multiphysics rigorous simulations,optimizing the front contact for realizing high performance.The numerical simulation was validated by fabricating PSCs optimized to reach high performance,energy conversion efficiency(ECE)=17.3%,open-circuit voltage(V_(OC))=1.08 V,short-circuit current density(J_(SC))=21.1 mA cm^(-2),and fillfactor(FF)=76%.Finally,a realistic front contact of nanophotonic architecture was proposed while improving broadband light absorption of the solar spectrum and light harvesting,resulting in enhanced quantum efficiency(QE).The nanophotonic PSC enables J_(SC)improvement by~17%while reducing the reflection by 12%,resulting in an estimated conversion efficiency over 23%.It is further demonstrated how the PSCs’UV-stability can be improved without considerably sacrificing optoelectronic performances.Particulars of nanophotonic designed ZnO:Cr front contact,PSCs device,and fabrication process are described.
