In recent years, with the emergence of non-fullerene fused-ring acceptors, power conversion efficiencies (PCEs) of organic solar cells (OSCs) have exceeded 19%.However, compared to inorganic or perovskite photovoltaic...In recent years, with the emergence of non-fullerene fused-ring acceptors, power conversion efficiencies (PCEs) of organic solar cells (OSCs) have exceeded 19%.However, compared to inorganic or perovskite photovoltaic cells, a higher voltage loss has become one of the key factors limiting further improvement in the PCEs of OSCs.The ternary/quaternary strategy has been identified as a feasible and effective way to obtain high-efficiency OSCs.In this review, a brief outline is given of the key roles that guest materials played in reducing voltage losses in solar cell devices and a brief look at the future material design and the design of ternary/quaternary systems.展开更多
A-DA'D-A type polymerized small-molecule acceptors(PSMAs) have very recently received wide attention because they possess advantages such as synthetic flexibility, narrowed bandgap, low energy loss, and impressive...A-DA'D-A type polymerized small-molecule acceptors(PSMAs) have very recently received wide attention because they possess advantages such as synthetic flexibility, narrowed bandgap, low energy loss, and impressive mechanical properties. With efforts on design and synthesis of PSMAs and polymer donors, significant progress has been made on all polymer solar cells(allPSCs) with power conversion efficiencies exceeding 18%. In this review, we focus on structure-property-performance relationships of the A-DA'D-A type PSMAs. First, we in-depth review the regio-random, regio-regular, and random ternary series by focusing on their structural modification such as from aspects of side-chains, halogenation, selenophene-containing and linkers, respectively. Second, we review the mechanically flexible and stretchable properties, which helps to find structural gene that correlates the mechanical properties. Third, we review the impressive small energy loss. In all, this review provides structural and material's clues, helpfully for designing high-performance all-PSCs.展开更多
Quaternary approach has been receiving more and more attention due to its effectiveness in improving solar cell performance, while synthesis/selection of the fourth component is yet a key issue. Herein, we report a ch...Quaternary approach has been receiving more and more attention due to its effectiveness in improving solar cell performance, while synthesis/selection of the fourth component is yet a key issue. Herein, we report a chlorinated phthalimide based donor polymer(namely Ph I-Cl) having an ultra-wide bandgap(2.10 e V) and a deep HOMO(-5.58 e V) level. Addition of Ph I-Cl as the third component of PM6:Y6 and the fourth of PM6:Y6:PC71BM increases both hole and electron mobilities and gives rise to more balanced charge carriers mobilities. Both the short-circuit current-density and fill-factor are increased and open-circuit voltage is well maintained, delivering 17.0% and 18.1% efficiencies, respectively. These results demonstrate that chlorination on the side thiophene of phthalimide-based donor polymer is a way to make deep HOMO and ultra-wide bandgap donor polymer guest used for highly efficient ternary and quaternary strategies.展开更多
The polymer/small-molecule electron donor and nonfullerene organic electron acceptor are of structural similarity with both donor and acceptor molecules consisting of polycyclic fused-ring backbone and being decorated...The polymer/small-molecule electron donor and nonfullerene organic electron acceptor are of structural similarity with both donor and acceptor molecules consisting of polycyclic fused-ring backbone and being decorated with alkyl-chains.In this study,we report that the introduction of binary fullerenes(C_(60)-/C_(70)-PCBM and C_(60)-/C_(70)-ICBA)into a nonfullerene binary system PBDB-T:ITIC reduces the polymer-nonfullerene acceptor intermixing,obtaining higher crystallinity with(100)crystal coherence length from 28 to 29–33 nm for the ITIC,and from 14 to 20–24 nm for the PBDB-T,and improved electron and hole mobilities both.Unprecedentedly,such a protocol reduces the ITIC optical band gap from 1.59 to 1.55 eV.As consequences,higher short-circuit current-density(17.8–18.4 vs.15.8 m A/cm^2),open-circuit voltage(0.92 vs.0.90 V)and fill-factor(0.72–0.73 vs.0.68)are simultaneously obtained,which ultimately afford higher efficient quaternary polymer solar cells with power conversion efficiencies(PCEs)up to 12.0%–12.8%comparing to the host binary device with 9.9%efficiency.For the polymer,ITIC,and ICBA/PCBM ternary blends,11%PCEs were recorded.The use of PCBM leads to larger red-shifting in thin film absorption and external quantum efficiency(EQE)response.Such effect is more pronounced when ICBA:PCBM mixture is used.These results indicate the size and shape of C_(60)and C_(70)as well as the substituent position of the second indene unit on C_(60)-/C_(70)-ICBA affect not only the blend morphology but also the electronic coupling in BHJ mixtures:the quaternary device performance increased in sequences of C_(70)-PCBM:C_(70)-ICBA→C_(70)-PCBM:C_(60)-ICBA→C_(60)-PCBM:C_(70)-ICBA→C_(60)-PCBM:C_(60)-ICBA.The resonant soft X-ray scattering(RSoXS)data indicated the most refined phase separation in the C_(60)-PCBM:C_(60)-ICBA based blend,corresponding to its best device function among the quaternary devices.These results indicate that the using of binary fullerenes as the acceptor additives allows for tuning nonfullerene blended film’s optical properties and filmmorphologies,shedding light on the designing high-performance multi-acceptor polymer solar cells.展开更多
Quaternary blended organic solar cells utilize four blended material components(one donor plus three acceptors, two donors and two acceptors, or three donors plus one acceptor) as the active layer materials. The use o...Quaternary blended organic solar cells utilize four blended material components(one donor plus three acceptors, two donors and two acceptors, or three donors plus one acceptor) as the active layer materials. The use of four material components allows us to have more material selections and more mechanism choices to improve the photon-to-electron conversion efficiency. In this contribution, we present a new case of quaternary material system, that shows 17.1% efficiency obtained by adding IDIC and PC71BM as the guest acceptors of the host binary of PM6:Y6. The lowest unoccupied molecular orbital(LUMO) levels of IDIC and PC71BM are both higher than that of Y6, which is one reason to obtain increased open-circuit voltage(Voc) in the quaternary device. Upon introduction of IDIC and PC71BM as the acceptor guests, the hole and electron mobilities are both increased, which contributes to the increased short-circuit current-density(Jsc). Effects of the weight ratios of the three acceptor components are investigated, which demonstrates that the increased hole and electron mobilities, the accelerated hole-transfer, and the reduced monomolecular recombination are the factors contributing to the increased Jscand fill-factor. This case of quaternary device demonstrates the applicability of the quaternary strategy in increasing the device functions and hence the efficiencies in the field of organic photovoltaic cells.展开更多
We report herein an efficient A^1-C=C-A^2-C=C-A^1 type small-molecule 4,4＇-difluoro-4-bora-3a,4a-diaza-sindacene （BODIPY） acceptor （A^1= BODIPY and A^2= diketopyrrolopyrrole （DPP）） by following the A-to-A excit...We report herein an efficient A^1-C=C-A^2-C=C-A^1 type small-molecule 4,4＇-difluoro-4-bora-3a,4a-diaza-sindacene （BODIPY） acceptor （A^1= BODIPY and A^2= diketopyrrolopyrrole （DPP）） by following the A-to-A excited electron delocalization via the BODIPY meso-position, the inherent directionality for the excited electron delocalization. The lowest unoccupied molecular orbital （LUMO） delocalizes across over whole the two flanking A^1 and the central A^2, and the highest occupied molecular orbital （HOMO） localizes dominantly on the -C=C-DPP-C=C- segment. The excited electron upon light excitation of the DPP segment delocalizes over both the BODIPY and DPP segments. The acceptor in chloroform shows an unprecedented plateau-like broad absorption between 550 and 700 nm with a large FWHM value of 195 nm. Upon transition into solid film, the acceptor shows absorption in the whole near ultraviolet-visible-near infrared wavelength region （300-830 nm） with a low band gap of 1.5 eV and a maximum absorptivity of 0.85 × 10^5 cm^-1. Introduction of the ethynyl spacer between the A^1 and A^2 and the close BODIPY-to-DPP LUMO energy levels are crucial for the excited n-electron delocalization across over whole the conjugation backbone. A power conversion efficiency of 6.60% was obtained from the ternary non-fullerene solar cell with PTB7-Th：p-DTS（FBTTh2）2 （0.5 ; 0.5） as the donor materials, which is the highest value among the non-fullerene organic solar cells with BODIPY as the electron acceptor material.展开更多
Recently, the fused-ring based low band gap （LBG） small molecule acceptors （SMAs） have emerged as efficient nonfullerene acceptors. So far, these LBG SMAs are mainly designed with IC （2-methylene-（3- （1,1 -dicy...Recently, the fused-ring based low band gap （LBG） small molecule acceptors （SMAs） have emerged as efficient nonfullerene acceptors. So far, these LBG SMAs are mainly designed with IC （2-methylene-（3- （1,1 -dicyanomethylene）indanone）） or its analogs, the benzo-type electron-accepting （A） units. Compared to benzene, thiophene is less aromatic and thus the thiophene-involving semiconducting molecule has more quinoidal character, which effectively reduces the energy gap between the highest occupied molecular orbit （HOMO） and the lowest unoccupied molecular orbit （LUMO）. Herein, we show that replacing the IC units in ITIC with the CT （cyclopenta[c]thiophen-4-one-5-methylene-6-（1,1-dicyano- methylene））, a thiophene-fused A unit, the quinoidal character is enhanced from 0.0353 on ITIC to 0.0349 on ITCT, the CT-ended SMA. The increase in the quinoidal character reduces the optical band gap and enhances the near IR absorptivity. When blended with the wide band gap （WBG） polymer donor, PBDB-T, an average power conversion efficiency of 10.99% is obtained with a short-circuit current-density （Jso） of 17.88 mA/cm2 and a fill-factor （FF） of 0.723. For comparisons, theJsc is of 16.92 mA/cm2, FF is of 0.655 and PCE is of 9.94% obtained from the ITIC：PBDB-T device. This case indicates that the replacement of the benzene ring on the IC unit with a more polarizable five-member ring such as thiophene is an effective way to enhance the absorption of the near IR solar photons towards designing high-performance nonfullerene polymer solar cells.展开更多
A new star-shaped molecule StOF-Br_3 containing oligofluorenes and halogen atoms(Bromine) has been synthesized and studied by Scanning Tunneling Microscopy(STM) at the highly oriented pyrolytic graphite(HOPG) surface....A new star-shaped molecule StOF-Br_3 containing oligofluorenes and halogen atoms(Bromine) has been synthesized and studied by Scanning Tunneling Microscopy(STM) at the highly oriented pyrolytic graphite(HOPG) surface.We have obtained the high-resolution self-assembled STM images,from which the highly ordered and closely packed non-porous arrangements of the StOF-Br_3 molecular selfassemblies at the heptanoic acid/HOPG surface could be observed.The molecular models and selfassembled StOF-Br_3 architectures have been given in the following text.Besides,we have also figured out the surface free energy by the density functional theory(DFT) calculation,which proved that the halogen...halogen interaction was strong enough to stabilize the ordered molecular self-assemblies.This work verifies the existence of bromine...bromine interactions,and meanwhile provides a kind of effective approach for quickly building ordered molecular nanoarchitectures with large areas and different geometries.展开更多
Non-fullerene organic acceptors have attracted increasing attention in recent years. One of the challenges in the synthesis of non-fullerene organic acceptors is to tune the absorption spectrum and molecular frontier ...Non-fullerene organic acceptors have attracted increasing attention in recent years. One of the challenges in the synthesis of non-fullerene organic acceptors is to tune the absorption spectrum and molecular frontier orbitals, affording low bandgap molecules with improved absorption of the near-infrared solar photons. In this paper, we present the synthesis, optoelectronic and photovoltaic properties of a series of dimeric perylene diimide(PDI) based non-fullerene acceptors. These PDI dimers are bridged by oligothiophene(T) from 1T to 6T. With the increase of the oligothienyl size, the highest occupied molecular orbital(HOMO) energy is raised from ?5.65 to ?5.10 e V, while that of the lowest unoccupied molecular orbit(LUMO) is kept constant at ?3.84 e V, affording narrow bandgap from 1.81 to 1.26 e V. The absorption from the oligothiophene occurs between 350 and 500 nm, which is complementary to that from its bridged PDI units, leading to a wide spectral coverage from 350 to 850 nm. The optimal dihedral angle between the bridged two perylene planes is dependent on the oligothienyl size, varying from 5° to 30°. The solubility of the dimers depends on the oligothienyl size and can be tuned by the alkyl chains on the bridged thienyl units. The possible applications as the solution-processable non-fullerene organic acceptor is primarily studied using commercial P3 HT as the blend donor. The photovoltaic results indicate that 1T, 4T and 6T all yield a higher efficiency of ?1.2%, whereas 2T, 3T and 5T all give a lower efficiency of <0.5%. The difference in the cell performance is related with the tradeoff between the differences of absorption, HOMO level and film-morphology between these dimers.展开更多
In this study,we report a new small molecule acceptor(named TT-4 F)which uses 3,6-dimethoxylthieno[3,2-b]thiophene(TT)as theπ-bridge.Addition of 0.05 weight ratio amount of TT-4 F into the host binary blend of PTB7-T...In this study,we report a new small molecule acceptor(named TT-4 F)which uses 3,6-dimethoxylthieno[3,2-b]thiophene(TT)as theπ-bridge.Addition of 0.05 weight ratio amount of TT-4 F into the host binary blend of PTB7-Th:IEICO-4 F,resulting in a ternary blend in a weight ratio of 1:1:0.05,enables increased open-circuit voltage(Voc),short-circuit curre nt-density(Jsc),and fill-factor(FF)at the same time.Finally,12.1%efficiency is obtained.Compared to the 3-(2-ethylhexyloxylthiophene)bridge on IEICO-4 F,the additional methoxyl group on the TT-6 position is involved in the lowest unoccupied molecular orbital(LUMO)and the largerπ-system on TT increases the electron-donating nature,both of which help to raise the LUMO level,one reason of the increased Voc.Upon addition of 0.05 TT-4 F,the hole mobility is increased,the monomolecular recombination is reduced,and the charge dissociation and collection is enhanced.All of these contribute to the increased Jsc and FF.展开更多
基金acknowledge the financial supports from the Department of Science and Technology of Inner Mongolia(No.2020GG0192)the Natural Science Foundation of Inner Mongolia(No.2022ZD04)+1 种基金the Inner Mongolia Normal University(No.112/1004031962)the Inner Mongolia Autonomous Region Postgraduate Research Innovation Fund(No.S20210274Z).
文摘In recent years, with the emergence of non-fullerene fused-ring acceptors, power conversion efficiencies (PCEs) of organic solar cells (OSCs) have exceeded 19%.However, compared to inorganic or perovskite photovoltaic cells, a higher voltage loss has become one of the key factors limiting further improvement in the PCEs of OSCs.The ternary/quaternary strategy has been identified as a feasible and effective way to obtain high-efficiency OSCs.In this review, a brief outline is given of the key roles that guest materials played in reducing voltage losses in solar cell devices and a brief look at the future material design and the design of ternary/quaternary systems.
基金the financial supports from the Department of Science and Technology of Inner Mongolia (No. 2020GG0192)the Natural Science Foundation of Inner Mongolia (No. 2022ZD04)the Inner Mongolia Normal University (No. 112/1004031962)。
文摘A-DA'D-A type polymerized small-molecule acceptors(PSMAs) have very recently received wide attention because they possess advantages such as synthetic flexibility, narrowed bandgap, low energy loss, and impressive mechanical properties. With efforts on design and synthesis of PSMAs and polymer donors, significant progress has been made on all polymer solar cells(allPSCs) with power conversion efficiencies exceeding 18%. In this review, we focus on structure-property-performance relationships of the A-DA'D-A type PSMAs. First, we in-depth review the regio-random, regio-regular, and random ternary series by focusing on their structural modification such as from aspects of side-chains, halogenation, selenophene-containing and linkers, respectively. Second, we review the mechanically flexible and stretchable properties, which helps to find structural gene that correlates the mechanical properties. Third, we review the impressive small energy loss. In all, this review provides structural and material's clues, helpfully for designing high-performance all-PSCs.
基金the financial support of the Department of Science and Technology of Inner Mongolia (No.2020GG0192)Grassland Talents (No. CYYC10031)+1 种基金Inner Mongolia Normal University (No. 112/1004031962)the financial support of Collaborative Innovation Center for Water Environment Security of Inner Mongolia Autonomous Region,China (No. XTCX003)。
文摘Quaternary approach has been receiving more and more attention due to its effectiveness in improving solar cell performance, while synthesis/selection of the fourth component is yet a key issue. Herein, we report a chlorinated phthalimide based donor polymer(namely Ph I-Cl) having an ultra-wide bandgap(2.10 e V) and a deep HOMO(-5.58 e V) level. Addition of Ph I-Cl as the third component of PM6:Y6 and the fourth of PM6:Y6:PC71BM increases both hole and electron mobilities and gives rise to more balanced charge carriers mobilities. Both the short-circuit current-density and fill-factor are increased and open-circuit voltage is well maintained, delivering 17.0% and 18.1% efficiencies, respectively. These results demonstrate that chlorination on the side thiophene of phthalimide-based donor polymer is a way to make deep HOMO and ultra-wide bandgap donor polymer guest used for highly efficient ternary and quaternary strategies.
基金supported by the National Natural Science Foundation of China (91433202, 21773262, 21327805, 21521062, 91227112)Chinese Academy of Sciences (XDB12010200)+1 种基金Ministry of Science and Technology of China (2013CB933503)the US Office of Naval Research (N00014-15-1-2244)
文摘The polymer/small-molecule electron donor and nonfullerene organic electron acceptor are of structural similarity with both donor and acceptor molecules consisting of polycyclic fused-ring backbone and being decorated with alkyl-chains.In this study,we report that the introduction of binary fullerenes(C_(60)-/C_(70)-PCBM and C_(60)-/C_(70)-ICBA)into a nonfullerene binary system PBDB-T:ITIC reduces the polymer-nonfullerene acceptor intermixing,obtaining higher crystallinity with(100)crystal coherence length from 28 to 29–33 nm for the ITIC,and from 14 to 20–24 nm for the PBDB-T,and improved electron and hole mobilities both.Unprecedentedly,such a protocol reduces the ITIC optical band gap from 1.59 to 1.55 eV.As consequences,higher short-circuit current-density(17.8–18.4 vs.15.8 m A/cm^2),open-circuit voltage(0.92 vs.0.90 V)and fill-factor(0.72–0.73 vs.0.68)are simultaneously obtained,which ultimately afford higher efficient quaternary polymer solar cells with power conversion efficiencies(PCEs)up to 12.0%–12.8%comparing to the host binary device with 9.9%efficiency.For the polymer,ITIC,and ICBA/PCBM ternary blends,11%PCEs were recorded.The use of PCBM leads to larger red-shifting in thin film absorption and external quantum efficiency(EQE)response.Such effect is more pronounced when ICBA:PCBM mixture is used.These results indicate the size and shape of C_(60)and C_(70)as well as the substituent position of the second indene unit on C_(60)-/C_(70)-ICBA affect not only the blend morphology but also the electronic coupling in BHJ mixtures:the quaternary device performance increased in sequences of C_(70)-PCBM:C_(70)-ICBA→C_(70)-PCBM:C_(60)-ICBA→C_(60)-PCBM:C_(70)-ICBA→C_(60)-PCBM:C_(60)-ICBA.The resonant soft X-ray scattering(RSoXS)data indicated the most refined phase separation in the C_(60)-PCBM:C_(60)-ICBA based blend,corresponding to its best device function among the quaternary devices.These results indicate that the using of binary fullerenes as the acceptor additives allows for tuning nonfullerene blended film’s optical properties and filmmorphologies,shedding light on the designing high-performance multi-acceptor polymer solar cells.
基金the National Natural Science Foundation of China(91433202,21773262,21327805)Taishan Scholars Program of Shandong Province(tsqn201812101).
文摘Quaternary blended organic solar cells utilize four blended material components(one donor plus three acceptors, two donors and two acceptors, or three donors plus one acceptor) as the active layer materials. The use of four material components allows us to have more material selections and more mechanism choices to improve the photon-to-electron conversion efficiency. In this contribution, we present a new case of quaternary material system, that shows 17.1% efficiency obtained by adding IDIC and PC71BM as the guest acceptors of the host binary of PM6:Y6. The lowest unoccupied molecular orbital(LUMO) levels of IDIC and PC71BM are both higher than that of Y6, which is one reason to obtain increased open-circuit voltage(Voc) in the quaternary device. Upon introduction of IDIC and PC71BM as the acceptor guests, the hole and electron mobilities are both increased, which contributes to the increased short-circuit current-density(Jsc). Effects of the weight ratios of the three acceptor components are investigated, which demonstrates that the increased hole and electron mobilities, the accelerated hole-transfer, and the reduced monomolecular recombination are the factors contributing to the increased Jscand fill-factor. This case of quaternary device demonstrates the applicability of the quaternary strategy in increasing the device functions and hence the efficiencies in the field of organic photovoltaic cells.
基金Supporting information for this article is available on the WWW under http：//dx.doi.org/10.1002/cjoc.201700542 or from the author. Dedicated to the Special Issue of Polymer Solar Cells.Acknowledgement The authors gratefully acknowledge the financial support ot＂ the National Natural Science Foundation of China （NSFC, Nos. 91433202, 21327805, 91227112 and 21221002）, Chinese Academy of Sciences （CAS, X DB12010200）, and Ministry of Science and Technol- ogy of the People＇s Republic of China （MOST, 2012YQ120060）. The authors gratefully acknowledge Beijing Synchrotron Radiation Facility （BSRF） for supports of GIXRD measurements.
文摘We report herein an efficient A^1-C=C-A^2-C=C-A^1 type small-molecule 4,4＇-difluoro-4-bora-3a,4a-diaza-sindacene （BODIPY） acceptor （A^1= BODIPY and A^2= diketopyrrolopyrrole （DPP）） by following the A-to-A excited electron delocalization via the BODIPY meso-position, the inherent directionality for the excited electron delocalization. The lowest unoccupied molecular orbital （LUMO） delocalizes across over whole the two flanking A^1 and the central A^2, and the highest occupied molecular orbital （HOMO） localizes dominantly on the -C=C-DPP-C=C- segment. The excited electron upon light excitation of the DPP segment delocalizes over both the BODIPY and DPP segments. The acceptor in chloroform shows an unprecedented plateau-like broad absorption between 550 and 700 nm with a large FWHM value of 195 nm. Upon transition into solid film, the acceptor shows absorption in the whole near ultraviolet-visible-near infrared wavelength region （300-830 nm） with a low band gap of 1.5 eV and a maximum absorptivity of 0.85 × 10^5 cm^-1. Introduction of the ethynyl spacer between the A^1 and A^2 and the close BODIPY-to-DPP LUMO energy levels are crucial for the excited n-electron delocalization across over whole the conjugation backbone. A power conversion efficiency of 6.60% was obtained from the ternary non-fullerene solar cell with PTB7-Th：p-DTS（FBTTh2）2 （0.5 ; 0.5） as the donor materials, which is the highest value among the non-fullerene organic solar cells with BODIPY as the electron acceptor material.
基金the financial support from the National Natural Science Foundation of China(NSFC, Nos. 91433202, 91227112 and 21221002)Chinese Academy of Sciences(CAS, No. XDB12010200)
文摘Recently, the fused-ring based low band gap （LBG） small molecule acceptors （SMAs） have emerged as efficient nonfullerene acceptors. So far, these LBG SMAs are mainly designed with IC （2-methylene-（3- （1,1 -dicyanomethylene）indanone）） or its analogs, the benzo-type electron-accepting （A） units. Compared to benzene, thiophene is less aromatic and thus the thiophene-involving semiconducting molecule has more quinoidal character, which effectively reduces the energy gap between the highest occupied molecular orbit （HOMO） and the lowest unoccupied molecular orbit （LUMO）. Herein, we show that replacing the IC units in ITIC with the CT （cyclopenta[c]thiophen-4-one-5-methylene-6-（1,1-dicyano- methylene））, a thiophene-fused A unit, the quinoidal character is enhanced from 0.0353 on ITIC to 0.0349 on ITCT, the CT-ended SMA. The increase in the quinoidal character reduces the optical band gap and enhances the near IR absorptivity. When blended with the wide band gap （WBG） polymer donor, PBDB-T, an average power conversion efficiency of 10.99% is obtained with a short-circuit current-density （Jso） of 17.88 mA/cm2 and a fill-factor （FF） of 0.723. For comparisons, theJsc is of 16.92 mA/cm2, FF is of 0.655 and PCE is of 9.94% obtained from the ITIC：PBDB-T device. This case indicates that the replacement of the benzene ring on the IC unit with a more polarizable five-member ring such as thiophene is an effective way to enhance the absorption of the near IR solar photons towards designing high-performance nonfullerene polymer solar cells.
基金The financial supports from the National Natural Science Foundation of China(NSFC,Nos.21773041 and 21327805)the National Basic Research Program of China(No.2016YFA0200700)。
文摘A new star-shaped molecule StOF-Br_3 containing oligofluorenes and halogen atoms(Bromine) has been synthesized and studied by Scanning Tunneling Microscopy(STM) at the highly oriented pyrolytic graphite(HOPG) surface.We have obtained the high-resolution self-assembled STM images,from which the highly ordered and closely packed non-porous arrangements of the StOF-Br_3 molecular selfassemblies at the heptanoic acid/HOPG surface could be observed.The molecular models and selfassembled StOF-Br_3 architectures have been given in the following text.Besides,we have also figured out the surface free energy by the density functional theory(DFT) calculation,which proved that the halogen...halogen interaction was strong enough to stabilize the ordered molecular self-assemblies.This work verifies the existence of bromine...bromine interactions,and meanwhile provides a kind of effective approach for quickly building ordered molecular nanoarchitectures with large areas and different geometries.
基金supported by the National Natural Science Foundation of China(2132780591227112+5 种基金9143320221221002)Chinese Academy of Sciences(XDB12010200)Ministry of Science and Technology of China(2011CB8084002013CB9335032012YQ120060)
文摘Non-fullerene organic acceptors have attracted increasing attention in recent years. One of the challenges in the synthesis of non-fullerene organic acceptors is to tune the absorption spectrum and molecular frontier orbitals, affording low bandgap molecules with improved absorption of the near-infrared solar photons. In this paper, we present the synthesis, optoelectronic and photovoltaic properties of a series of dimeric perylene diimide(PDI) based non-fullerene acceptors. These PDI dimers are bridged by oligothiophene(T) from 1T to 6T. With the increase of the oligothienyl size, the highest occupied molecular orbital(HOMO) energy is raised from ?5.65 to ?5.10 e V, while that of the lowest unoccupied molecular orbit(LUMO) is kept constant at ?3.84 e V, affording narrow bandgap from 1.81 to 1.26 e V. The absorption from the oligothiophene occurs between 350 and 500 nm, which is complementary to that from its bridged PDI units, leading to a wide spectral coverage from 350 to 850 nm. The optimal dihedral angle between the bridged two perylene planes is dependent on the oligothienyl size, varying from 5° to 30°. The solubility of the dimers depends on the oligothienyl size and can be tuned by the alkyl chains on the bridged thienyl units. The possible applications as the solution-processable non-fullerene organic acceptor is primarily studied using commercial P3 HT as the blend donor. The photovoltaic results indicate that 1T, 4T and 6T all yield a higher efficiency of ?1.2%, whereas 2T, 3T and 5T all give a lower efficiency of <0.5%. The difference in the cell performance is related with the tradeoff between the differences of absorption, HOMO level and film-morphology between these dimers.
基金financial support from the National Natural Science Foundation of China(NSFC,Nos.91433202,21773262 and 21327805)Natural Science Foundation of Hebei Province(No.B2016201014)。
文摘In this study,we report a new small molecule acceptor(named TT-4 F)which uses 3,6-dimethoxylthieno[3,2-b]thiophene(TT)as theπ-bridge.Addition of 0.05 weight ratio amount of TT-4 F into the host binary blend of PTB7-Th:IEICO-4 F,resulting in a ternary blend in a weight ratio of 1:1:0.05,enables increased open-circuit voltage(Voc),short-circuit curre nt-density(Jsc),and fill-factor(FF)at the same time.Finally,12.1%efficiency is obtained.Compared to the 3-(2-ethylhexyloxylthiophene)bridge on IEICO-4 F,the additional methoxyl group on the TT-6 position is involved in the lowest unoccupied molecular orbital(LUMO)and the largerπ-system on TT increases the electron-donating nature,both of which help to raise the LUMO level,one reason of the increased Voc.Upon addition of 0.05 TT-4 F,the hole mobility is increased,the monomolecular recombination is reduced,and the charge dissociation and collection is enhanced.All of these contribute to the increased Jsc and FF.
