Revealing the charge generation is a crucial step to understand the organic photovoltaics. Recent development in non-fullerene organic solar cells （OSCs） indicates efficient charge separation even with negligible en...Revealing the charge generation is a crucial step to understand the organic photovoltaics. Recent development in non-fullerene organic solar cells （OSCs） indicates efficient charge separation even with negligible energetic offset between the donor and acceptor materials. These new findings trigger a critical question concerning the charge separation mechanism in OSCs, traditionally believed to result from sufficient energetic offset between the polymer donor and fullerene acceptor. We propose a new mechanism, which involves the molecular electrostatic potential, to explain efficient charge separation in non-fullerene OSCs. Together with the new mechanism, we demonstrate a record efficiency of -12% for systems with negligible energetic offset between donor and acceptor materials. Our analysis also rationalizes different requirement of the energetic offset between fullerene-based and non-fullerene OSCs, and paves the way for further design of OSC materials with both high photocurrent and high photovottage at the same time.展开更多
For the process of photovoltaic conversion in organic solar cells(OSCs)and quantum-dot solar cells(QDSCs),three of four steps are determined by exciton behavior,namely,exciton generation,exciton diffusion,and exciton ...For the process of photovoltaic conversion in organic solar cells(OSCs)and quantum-dot solar cells(QDSCs),three of four steps are determined by exciton behavior,namely,exciton generation,exciton diffusion,and exciton dissociation.Therefore,it is of great importance to regulate exciton behavior in OSCs and QDSCs for achieving high power conversion efficiency.Due to the rapid development in materials and device fabrication,great progress has been made to manage the exciton behavior to achieve prolonged exciton diffusion length and improved exciton dissociation in recent years.In this review,we first introduce the parameters that affect exciton behavior,followed by the methods to measure exciton diffusion length.Then,we provide an overview of the recent advances with regard to exciton behavior investigation in OSCs and QDSCs,including exciton lifetime,exciton diffusion coefficient,and exciton dissociation.Finally,we propose future directions in deepening the understanding of exciton behavior and boosting the performance of OSCs and QDSCs.展开更多
设计和合成结构新颖的聚合物太阳能电池给体材料是有机电子学的热点研究领域.首先利用二噻吩取代的苯并二噻吩(DBDT)作为富电子结构单元,吡咯并吡咯二酮(DPP)作为缺电子单元构筑了一种新的聚合物太阳能电池电子给体材料(PDBDTDPP),然后...设计和合成结构新颖的聚合物太阳能电池给体材料是有机电子学的热点研究领域.首先利用二噻吩取代的苯并二噻吩(DBDT)作为富电子结构单元,吡咯并吡咯二酮(DPP)作为缺电子单元构筑了一种新的聚合物太阳能电池电子给体材料(PDBDTDPP),然后以[6,6]-苯基-C61-丁酸甲酯(PC61BM)作为电子受体,借助密度泛函理论(DFT)方法结合不相干的Marcus-Hush电荷传输模型,系统研究了PC61BM-DBDTDPPn=1,2,3,∞体系的分子结构、电子性质、光吸收性质、电荷转移的内重组能和外重组能、激子结合能、电荷传输积分、给体-受体界面上激子分离和电荷复合速率等性质,并利用线性回归方法分析了聚合物重复单元与其光伏性质的关系.结果表明,该聚合物具有较好的平面结构,低的最高占据分子轨道(HOMO)能级,在紫外-可见区具有宽且强的光学吸收、较大的激子束缚能(1.365 e V),小的激子分离内重组能(0.152 e V)和电荷复合内重组能(0.314 e V).在给体-受体界面上,激子分离速率高达1.073×1014 s-1,而电荷复合速率仅为1.797×108 s-1.相比较而言,激子分离速率比电荷复合速率高约6个数量级,表明在给体-受体界面上,光生激子具有很高的分离效率.总之,研究证明PDBDTDPP是一个非常有前途的聚合物太阳能电池给体材料,值得实验上进一步合成及器件化研究.理论研究不仅有助于更深入理解有机化合物结构与其光学、电子性质之间的关系,还可以为合理设计聚合物太阳能电池给体材料提供有价值的参考.展开更多
Perovskite quantum dots(PQDs) hold immense potential as photocatalysts for CO_(2) reduction due to their remarkable quantum properties,which facilitates the generation of multiple excitons,providing the necessary high...Perovskite quantum dots(PQDs) hold immense potential as photocatalysts for CO_(2) reduction due to their remarkable quantum properties,which facilitates the generation of multiple excitons,providing the necessary high-energy electrons for CO_(2) photoreduction.However,harnessing multi-excitons in PQDs for superior photocatalysis remains challenging,as achieving the concurrent dissociation of excitons and interparticle energy transfer proves elusive.This study introduces a ligand density-controlled strategy to enhance both exciton dissociation and interparticle energy transfer in CsPbBr_(3) PQDs.Optimized CsPbBr_(3) PQDs with the regulated ligand density exhibit efficient photocatalytic conversion of CO_(2) to CO,achieving a 2.26-fold improvement over unoptimized counterparts while maintaining chemical integrity.Multiple analytical techniques,including Kelvin probe force microscopy,temperaturedependent photoluminescence,femtosecond transient absorption spectroscopy,and density functional theory calculations,collectively affirm that the proper ligand termination promotes the charge separation and the interparticle transfer through ligand-mediated interfacial electron coupling and electronic interactions.This work reveals ligand density-dependent variations in the gas-solid photocatalytic CO_(2) reduction performance of CsPbBr_(3) PQDs,underscoring the importance of ligand engineering for enhancing quantum dot photocatalysis.展开更多
Solar-to-H2 conversion is attracting much research attention as a potential approach to meet global renewable energy demands. Although significant advances have been made using metal-tipped colloidal cadmium chalcogen...Solar-to-H2 conversion is attracting much research attention as a potential approach to meet global renewable energy demands. Although significant advances have been made using metal-tipped colloidal cadmium chalcogenide zero-dimensional （0D） quantum dots and one-dimensional （1D） nanorod heterostructures in solar-to-H2 conversion, their efficiency may be further enhanced using an emerging class of colloidal cadmium chalcogenide nanocrystals, namely two-dimensional （2D） nanoplatelets （NPLs）, because of their unique properties. In this review, we summarize the recent advances on exciton dissociation dynamics and light-driven H2 generation performance of colloidal nanoplatelet heterostructures. Following an introduction on the electronic structure of 2D NPLs, we discuss the dynamics of exciton dissociation by electron transfer to molecular acceptors. The exciton quenching dynamics of CdS NPL-Pt and CdSe NPL-Pt heterostructures are compared to highlight the effect of material properties on the relative contributions of the energy-transfer and electron- transfer pathways. Representative solar-to-H2 conversion performances of 2D NPL-metal heterostructures are discussed and compared with those of 1D nanorod-metal heterostructures. Finally, we discuss the challenges in further improving the solar-to-fuel conversion efficiencies of these systems.展开更多
Coupling graphitic carbon nitride(CN)with carbonaceous materials is an effective strategy to improve photocatalytic performance,but the contributions of carbonaceous materials are not fully understood.Herein,a new typ...Coupling graphitic carbon nitride(CN)with carbonaceous materials is an effective strategy to improve photocatalytic performance,but the contributions of carbonaceous materials are not fully understood.Herein,a new type of carbon/CN(CCN)complex photocatalyst is synthesized with a 6-fold enhancement of H2 evolution rate compared to that of pristine CN.The role of carbon in photocatalytic H2 evolution reaction is systemically studied and it is experimentally and theoretically revealed that carbon mainly contributes to the improved capability of exciton dissociation and enhanced electric conductivity for charge transfer,leading to an increased population of photo-carriers for photocatalytic reactions.Interestingly,the enhanced light absorption originated from carbon barely generates charge carriers for H2 evolution activity.These new findings will inspire the rational design of carbon-based photocatalysts for efficient solar fuel production.展开更多
The strong intrinsic Coulomb interactions of Frenkel excitons in crystalline carbon nitride(CCN) greatly limits their dissociation into electrons and holes, resulting in unsatisfactory charges separation and photocata...The strong intrinsic Coulomb interactions of Frenkel excitons in crystalline carbon nitride(CCN) greatly limits their dissociation into electrons and holes, resulting in unsatisfactory charges separation and photocatalytic efficiency. Herein, we propose a strategy to facilitate excitons dissociation by molecular regulation induced built-in electric field(BIEF). The electron-rich pyrimidine-ring into CCN changes the charge density distribution over heptazine-rings to induce BIEF between melon chains. Such BIEF is sufficient to overcome the considerable exciton binding energy(EBE) and reduce it from 38.4 meV to 16.4 meV,increasing the excitons dissociation efficiency(EDE) from 21.5% to 51.9%. Our results establish a strategy to facilitate excitons dissociation through molecular regulation induced BIEF, targeting the intrinsic high EBE and low EDE of polymer photocatalysts.展开更多
Understanding excitonic processes at organic heterojunctions is crucial for development of organic semiconductor devices. This article reviews recent research on excitonic physics that involve intermolecular charge tr...Understanding excitonic processes at organic heterojunctions is crucial for development of organic semiconductor devices. This article reviews recent research on excitonic physics that involve intermolecular charge transfer （CT） excitons, and progress on understanding relationships between various interface energy levels and key parameters governing various competing interface excitonic processes. These interface excitonic processes include radiative exciplex emission, nonradiative recombination, Auger electron emission, and CT exciton dissociation. This article also reviews various device applications involving interface CT excitons, such as organic light-emitting diodes （OLEDs）, organic photovoltaic cells, organic rectifying diodes, and ultralow-voltage Auger OLEDs.展开更多
The fabrication of multifunctional electronic devices based on the intriguing natures of organic semiconductors is crucial for organic electronics.Ultranarrow-bandgap materials are in urgent demand for fabricating hig...The fabrication of multifunctional electronic devices based on the intriguing natures of organic semiconductors is crucial for organic electronics.Ultranarrow-bandgap materials are in urgent demand for fabricating high-performance organic photovoltaic(OPV)cells and highly sensitive near-infrared organic photodetectors(OPDs).By combining alkoxy modification and an asymmetric strategy,three narrowbandgap electronic acceptors(BTP-4F,DO-4F,and QO-4F)were synthesized with finely tuned molecular electrostatic potential(ESP)distributions.Through the careful modulation of electronic configurations,the optical absorption onsets of DO-4F and QO-4F exceeded 1μm.The experimental and theoretical results suggest that the small ESP of QO-4F is beneficial for achieving a low nonradiative voltage loss,while the large ESP of BTP-4F can help obtain high exciton dissociation efficiency.By contrast,the asymmetric acceptor DO-4F with a moderate ESP possesses balanced voltage loss and exciton dissociation,yielding the best power conversion efficiency of 13.6%in the OPV cells.OPDs were also fabricated based on the combination of PBDB-T:DO-4F,and the as-fabricated device outputs a high shot-noise-limited specific detectivity of 3.05×10^(13) Jones at 850 nm,which is a very good result for near-infrared OPDs.This work is anticipated to provide a rational way of designing high-performance ultranarrow-bandgap organic semiconductors by modulating the molecular ESP.展开更多
We analytically and numerically compute the Onsager dissociation rate(exciton dissociation)on an interface induced by a piezoelectric potential in an inorganicorganic hybrid p-n junction system(ZnO+(poly(p-phenylene v...We analytically and numerically compute the Onsager dissociation rate(exciton dissociation)on an interface induced by a piezoelectric potential in an inorganicorganic hybrid p-n junction system(ZnO+(poly(p-phenylene vinylene));PPV).When a positive piezoelectric potential is created at the interface region owing to the deformation of the system,free electrons accumulate at the interface.Hence,screening effects are observed.It is assumed that the electron layer formed at the interface then attracts free holes from the p-type PPV region,which leads to exciton formation,possibly via the Langevin recombination process.The increased exciton density can then contribute to the Onsager dissociation rate,which is maximum around the interface.This paper focuses on the role of piezoelectric effects in promoting exciton formation at the interface and its relation with the exciton dissociation rate.展开更多
基金J. Hou acknowledge financial support from National Natural Science Foundation of China （91633301, 51673201, 91333204）, the Ministry of Science and Technology of China （2014CB643501） and the Chinese Academy of Sciences （XDB12030200）. F. Gao and D. Qian would like to acknowledge the Swedish Research Council VR （Grant No. 2017-007444 the Swedish Energy Agency Ener- gimyndigheten （2016-010174）, the Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University （Faculty Grant No. SFO-Mat-LiU #2009- 00971）.
文摘Revealing the charge generation is a crucial step to understand the organic photovoltaics. Recent development in non-fullerene organic solar cells （OSCs） indicates efficient charge separation even with negligible energetic offset between the donor and acceptor materials. These new findings trigger a critical question concerning the charge separation mechanism in OSCs, traditionally believed to result from sufficient energetic offset between the polymer donor and fullerene acceptor. We propose a new mechanism, which involves the molecular electrostatic potential, to explain efficient charge separation in non-fullerene OSCs. Together with the new mechanism, we demonstrate a record efficiency of -12% for systems with negligible energetic offset between donor and acceptor materials. Our analysis also rationalizes different requirement of the energetic offset between fullerene-based and non-fullerene OSCs, and paves the way for further design of OSC materials with both high photocurrent and high photovottage at the same time.
基金The authors thank the National Natural Science Foundation of China(Nos.52173189,22105208,61935017)Hunan Provincial Natural Science Foundation of China(No.2022JJ40570)+2 种基金the Science and Technology Development Fund,Macao SAR(No.FDCT-0044/2020/A1)UM's Research Fund(No.MYRG2020-00151-IAPME)Shenzhen Institute of Advanced Technology,and the Chinese Academy of Sciences for financial support.
文摘For the process of photovoltaic conversion in organic solar cells(OSCs)and quantum-dot solar cells(QDSCs),three of four steps are determined by exciton behavior,namely,exciton generation,exciton diffusion,and exciton dissociation.Therefore,it is of great importance to regulate exciton behavior in OSCs and QDSCs for achieving high power conversion efficiency.Due to the rapid development in materials and device fabrication,great progress has been made to manage the exciton behavior to achieve prolonged exciton diffusion length and improved exciton dissociation in recent years.In this review,we first introduce the parameters that affect exciton behavior,followed by the methods to measure exciton diffusion length.Then,we provide an overview of the recent advances with regard to exciton behavior investigation in OSCs and QDSCs,including exciton lifetime,exciton diffusion coefficient,and exciton dissociation.Finally,we propose future directions in deepening the understanding of exciton behavior and boosting the performance of OSCs and QDSCs.
文摘设计和合成结构新颖的聚合物太阳能电池给体材料是有机电子学的热点研究领域.首先利用二噻吩取代的苯并二噻吩(DBDT)作为富电子结构单元,吡咯并吡咯二酮(DPP)作为缺电子单元构筑了一种新的聚合物太阳能电池电子给体材料(PDBDTDPP),然后以[6,6]-苯基-C61-丁酸甲酯(PC61BM)作为电子受体,借助密度泛函理论(DFT)方法结合不相干的Marcus-Hush电荷传输模型,系统研究了PC61BM-DBDTDPPn=1,2,3,∞体系的分子结构、电子性质、光吸收性质、电荷转移的内重组能和外重组能、激子结合能、电荷传输积分、给体-受体界面上激子分离和电荷复合速率等性质,并利用线性回归方法分析了聚合物重复单元与其光伏性质的关系.结果表明,该聚合物具有较好的平面结构,低的最高占据分子轨道(HOMO)能级,在紫外-可见区具有宽且强的光学吸收、较大的激子束缚能(1.365 e V),小的激子分离内重组能(0.152 e V)和电荷复合内重组能(0.314 e V).在给体-受体界面上,激子分离速率高达1.073×1014 s-1,而电荷复合速率仅为1.797×108 s-1.相比较而言,激子分离速率比电荷复合速率高约6个数量级,表明在给体-受体界面上,光生激子具有很高的分离效率.总之,研究证明PDBDTDPP是一个非常有前途的聚合物太阳能电池给体材料,值得实验上进一步合成及器件化研究.理论研究不仅有助于更深入理解有机化合物结构与其光学、电子性质之间的关系,还可以为合理设计聚合物太阳能电池给体材料提供有价值的参考.
基金supported by the National Natural Science Foundation of China (22225606, 22261142663, and 22176029)the Sichuan Science and Technology Program (2022JDRC0084 and 2021JDJQ0006)the CMA Key Open Laboratory of Transforming Climate Resources to Economy (2023005K)。
文摘Perovskite quantum dots(PQDs) hold immense potential as photocatalysts for CO_(2) reduction due to their remarkable quantum properties,which facilitates the generation of multiple excitons,providing the necessary high-energy electrons for CO_(2) photoreduction.However,harnessing multi-excitons in PQDs for superior photocatalysis remains challenging,as achieving the concurrent dissociation of excitons and interparticle energy transfer proves elusive.This study introduces a ligand density-controlled strategy to enhance both exciton dissociation and interparticle energy transfer in CsPbBr_(3) PQDs.Optimized CsPbBr_(3) PQDs with the regulated ligand density exhibit efficient photocatalytic conversion of CO_(2) to CO,achieving a 2.26-fold improvement over unoptimized counterparts while maintaining chemical integrity.Multiple analytical techniques,including Kelvin probe force microscopy,temperaturedependent photoluminescence,femtosecond transient absorption spectroscopy,and density functional theory calculations,collectively affirm that the proper ligand termination promotes the charge separation and the interparticle transfer through ligand-mediated interfacial electron coupling and electronic interactions.This work reveals ligand density-dependent variations in the gas-solid photocatalytic CO_(2) reduction performance of CsPbBr_(3) PQDs,underscoring the importance of ligand engineering for enhancing quantum dot photocatalysis.
文摘Solar-to-H2 conversion is attracting much research attention as a potential approach to meet global renewable energy demands. Although significant advances have been made using metal-tipped colloidal cadmium chalcogenide zero-dimensional （0D） quantum dots and one-dimensional （1D） nanorod heterostructures in solar-to-H2 conversion, their efficiency may be further enhanced using an emerging class of colloidal cadmium chalcogenide nanocrystals, namely two-dimensional （2D） nanoplatelets （NPLs）, because of their unique properties. In this review, we summarize the recent advances on exciton dissociation dynamics and light-driven H2 generation performance of colloidal nanoplatelet heterostructures. Following an introduction on the electronic structure of 2D NPLs, we discuss the dynamics of exciton dissociation by electron transfer to molecular acceptors. The exciton quenching dynamics of CdS NPL-Pt and CdSe NPL-Pt heterostructures are compared to highlight the effect of material properties on the relative contributions of the energy-transfer and electron- transfer pathways. Representative solar-to-H2 conversion performances of 2D NPL-metal heterostructures are discussed and compared with those of 1D nanorod-metal heterostructures. Finally, we discuss the challenges in further improving the solar-to-fuel conversion efficiencies of these systems.
基金support from Australian Research Council(ARC)through the Discovery and Laureate Fellowship programs is greatly acknowledged.
文摘Coupling graphitic carbon nitride(CN)with carbonaceous materials is an effective strategy to improve photocatalytic performance,but the contributions of carbonaceous materials are not fully understood.Herein,a new type of carbon/CN(CCN)complex photocatalyst is synthesized with a 6-fold enhancement of H2 evolution rate compared to that of pristine CN.The role of carbon in photocatalytic H2 evolution reaction is systemically studied and it is experimentally and theoretically revealed that carbon mainly contributes to the improved capability of exciton dissociation and enhanced electric conductivity for charge transfer,leading to an increased population of photo-carriers for photocatalytic reactions.Interestingly,the enhanced light absorption originated from carbon barely generates charge carriers for H2 evolution activity.These new findings will inspire the rational design of carbon-based photocatalysts for efficient solar fuel production.
基金jointly supported by the Natural Science Foundation of China(Nos.51874199,22078200,22102103)the grant from SZIIT(No.SZIIT2022KJ026)+1 种基金Guangdong Basic and Applied Basic Research Foundation(Nos.2019A1515111021,2021A1515010162)Shenzhen Innovation Program(No.JCYJ20170818142642395)。
文摘The strong intrinsic Coulomb interactions of Frenkel excitons in crystalline carbon nitride(CCN) greatly limits their dissociation into electrons and holes, resulting in unsatisfactory charges separation and photocatalytic efficiency. Herein, we propose a strategy to facilitate excitons dissociation by molecular regulation induced built-in electric field(BIEF). The electron-rich pyrimidine-ring into CCN changes the charge density distribution over heptazine-rings to induce BIEF between melon chains. Such BIEF is sufficient to overcome the considerable exciton binding energy(EBE) and reduce it from 38.4 meV to 16.4 meV,increasing the excitons dissociation efficiency(EDE) from 21.5% to 51.9%. Our results establish a strategy to facilitate excitons dissociation through molecular regulation induced BIEF, targeting the intrinsic high EBE and low EDE of polymer photocatalysts.
基金supported by the National Natural Science Foundation of China(Grant No.U1402273)the Natural Science and Engineering Research Council of Canada
文摘Understanding excitonic processes at organic heterojunctions is crucial for development of organic semiconductor devices. This article reviews recent research on excitonic physics that involve intermolecular charge transfer （CT） excitons, and progress on understanding relationships between various interface energy levels and key parameters governing various competing interface excitonic processes. These interface excitonic processes include radiative exciplex emission, nonradiative recombination, Auger electron emission, and CT exciton dissociation. This article also reviews various device applications involving interface CT excitons, such as organic light-emitting diodes （OLEDs）, organic photovoltaic cells, organic rectifying diodes, and ultralow-voltage Auger OLEDs.
基金the support from the National Natural Science Foundation of China(NSFC,21835006)the financial support from the NSFC(22075301 and 22122905)+2 种基金the Youth Innovation Promotion Association CAS(2018043)the Key Research Program of the Chinese Academy of Sciences,Grant NO.XDPB13-3supported by the Beijing National Laboratory for Molecular Sciences(BNLMS-CXXM-201903)。
文摘The fabrication of multifunctional electronic devices based on the intriguing natures of organic semiconductors is crucial for organic electronics.Ultranarrow-bandgap materials are in urgent demand for fabricating high-performance organic photovoltaic(OPV)cells and highly sensitive near-infrared organic photodetectors(OPDs).By combining alkoxy modification and an asymmetric strategy,three narrowbandgap electronic acceptors(BTP-4F,DO-4F,and QO-4F)were synthesized with finely tuned molecular electrostatic potential(ESP)distributions.Through the careful modulation of electronic configurations,the optical absorption onsets of DO-4F and QO-4F exceeded 1μm.The experimental and theoretical results suggest that the small ESP of QO-4F is beneficial for achieving a low nonradiative voltage loss,while the large ESP of BTP-4F can help obtain high exciton dissociation efficiency.By contrast,the asymmetric acceptor DO-4F with a moderate ESP possesses balanced voltage loss and exciton dissociation,yielding the best power conversion efficiency of 13.6%in the OPV cells.OPDs were also fabricated based on the combination of PBDB-T:DO-4F,and the as-fabricated device outputs a high shot-noise-limited specific detectivity of 3.05×10^(13) Jones at 850 nm,which is a very good result for near-infrared OPDs.This work is anticipated to provide a rational way of designing high-performance ultranarrow-bandgap organic semiconductors by modulating the molecular ESP.
基金This research was supported by the Office of the Theory&Modeling Based Design of Energy Harvesting,Korea.
文摘We analytically and numerically compute the Onsager dissociation rate(exciton dissociation)on an interface induced by a piezoelectric potential in an inorganicorganic hybrid p-n junction system(ZnO+(poly(p-phenylene vinylene));PPV).When a positive piezoelectric potential is created at the interface region owing to the deformation of the system,free electrons accumulate at the interface.Hence,screening effects are observed.It is assumed that the electron layer formed at the interface then attracts free holes from the p-type PPV region,which leads to exciton formation,possibly via the Langevin recombination process.The increased exciton density can then contribute to the Onsager dissociation rate,which is maximum around the interface.This paper focuses on the role of piezoelectric effects in promoting exciton formation at the interface and its relation with the exciton dissociation rate.
