Donor-acceptor(D-A)conjugated oligomers exhibit unique advantages in optoelectronic materials due to their well-defined molecular structures and ease of purification.However,current D-A oligomers incorporating electro...Donor-acceptor(D-A)conjugated oligomers exhibit unique advantages in optoelectronic materials due to their well-defined molecular structures and ease of purification.However,current D-A oligomers incorporating electron-deficient units like benzothiadiazole(BTz)and naphthobisthiadiazole(NTz)are largely restricted to linear configurations.In this study,two novel D-A conjugated oligomers(VG1 and VG2)with zigzag-shaped topological structures were designed and synthesized by integrating the electron-donating indacenodithiophene(IDT)unit with the previously developed strong electronwithdrawing triphenylenobisthiadiazole(TPTz)unit.Due to the unique V-shaped structure of TPTz unit,VG2 demonstrates a slightly reduced bandgap by 0.04 eV as the number of repeating units increases,while its light absorption coefficient is significantly enhanced.When applied to organic photovoltaic devices,the VG2:Y6-based device achieves a power conversion efficiency(PCE)of 2.56%,outperforming the VG1:Y6 system(2.37%).This improvement is attributed to the reduced radiative recombination losses below the bandgap and lower non-radiative energy losses in the VG2:Y6 device.This work offers a new strategy for modulating the topological structure of conjugated oligomers and their optoelectronic properties.展开更多
Currently,the polymer PM6 stands out as one of the most efficient donor polymers in the field of organic solar cells,and many researchers are dedicated to further enhancing its photovoltaic performance.Among various s...Currently,the polymer PM6 stands out as one of the most efficient donor polymers in the field of organic solar cells,and many researchers are dedicated to further enhancing its photovoltaic performance.Among various strategies,the end-capping modification was a simple and effective way to minimize the undesired end-capping impurity groups and to narrow the molecular weight distribution of the final polymer donors.In this study,we systematically investigated the substitution effect of H,F,and Cl of the end-capping naphthyl group of the PM6 polymer on the photovoltaic performance.Compared to the naphthyl and fluoronaphthyl group,the chloro-naphthyl moiety possesses a larger dipole moment,thereby enhancing the interaction between chloro-naphthyl end-capped PM6 with the small molecule acceptor,L8-BO,significantly reducing theπ-πstacking distances between molecules and enhancing charge-carrier mobilities.Devices based on PM6-Cl:L8-BO exhibited appropriate phase separation,optimal molecular orientation,and minimal charge recombination.Consequently,the PM6-Cl:L8-BO-based device achieved an outstanding power conversion efficiency of 18.07%,with simultaneous enhancements in short-circuit current density(J_(SC))and fill factor(FF).This was much higher than those of PM6-F:L8-BO-based(17.60%)and PM6-H:L8-BO-based(16.87%)devices.These results demonstrated that the modulation of end-capped atoms in PM6 could significantly improve the photovoltaic performance of organic solar cells and provide guidance for the design and synthesis of highperformance polymers.展开更多
Ionomer impregnation represents a milestone in the evolution of polymer electrolyte fuel cell （PEFC） catalyst layers. Ionomer acts as the binder, facilitates proton transport, and thereby drastically improves cataly...Ionomer impregnation represents a milestone in the evolution of polymer electrolyte fuel cell （PEFC） catalyst layers. Ionomer acts as the binder, facilitates proton transport, and thereby drastically improves catalyst utilization and effectiveness. However, advanced morpho- logical and functional characterizations have revealed that up to 60% of Pt nanoparticles can be trapped in the micropores of carbon support particles. Ionomer clusters and oxygen molecules can hardly enter into micropores, leading to low Pt utilization and effectiveness. Moreover, the ionomer thin-films covering Pt nanoparticles can cause significant mass transport loss especially at high current densities. Ionomer-free ultra-thin catalyst layers （UTCLs） emerge as a promising alternative to reduce Pt loading by improving catalyst utilization and effectiveness, while theoretical issues such as the proton conduction mechan- ism remain puzzling and practical issues such as the rather narrow operation window remain unsettled. At present, the development of PEFC catalyst layer has come to a crossroads： staying ionomer-impregnated or going iono- mer-free. It is always beneficial to look back into the past when coming to a crossroads. This paper addresses the characterization and modeling of both the conventional ionomer-impregnated catalyst layer and the emerging ionomer-free UTCLs, featuring advances in characterizing microscale distributions of Pt particles, ionomer, support particles and unraveling their interactions; advances in fundamental understandings of proton conduction and flooding behaviors in ionomer-free UTCLs; advances in modeling of conventional catalyst layers and especially UTCLs; and discussions on high-impact research topics in characterizing and modeling of catalyst layers.展开更多
文摘Donor-acceptor(D-A)conjugated oligomers exhibit unique advantages in optoelectronic materials due to their well-defined molecular structures and ease of purification.However,current D-A oligomers incorporating electron-deficient units like benzothiadiazole(BTz)and naphthobisthiadiazole(NTz)are largely restricted to linear configurations.In this study,two novel D-A conjugated oligomers(VG1 and VG2)with zigzag-shaped topological structures were designed and synthesized by integrating the electron-donating indacenodithiophene(IDT)unit with the previously developed strong electronwithdrawing triphenylenobisthiadiazole(TPTz)unit.Due to the unique V-shaped structure of TPTz unit,VG2 demonstrates a slightly reduced bandgap by 0.04 eV as the number of repeating units increases,while its light absorption coefficient is significantly enhanced.When applied to organic photovoltaic devices,the VG2:Y6-based device achieves a power conversion efficiency(PCE)of 2.56%,outperforming the VG1:Y6 system(2.37%).This improvement is attributed to the reduced radiative recombination losses below the bandgap and lower non-radiative energy losses in the VG2:Y6 device.This work offers a new strategy for modulating the topological structure of conjugated oligomers and their optoelectronic properties.
基金supported by the National Natural Science Foundation of China(NSFC)(52203249)the Young Innovation Leading Talents of Suzhou Innovation and Entrepreneurship Leading Talents Program(ZXL2022462)the Suzhou Institute of Nano-Tech and Nano-Bionics,Chinese Academy of Sciences(E1511401)。
文摘Currently,the polymer PM6 stands out as one of the most efficient donor polymers in the field of organic solar cells,and many researchers are dedicated to further enhancing its photovoltaic performance.Among various strategies,the end-capping modification was a simple and effective way to minimize the undesired end-capping impurity groups and to narrow the molecular weight distribution of the final polymer donors.In this study,we systematically investigated the substitution effect of H,F,and Cl of the end-capping naphthyl group of the PM6 polymer on the photovoltaic performance.Compared to the naphthyl and fluoronaphthyl group,the chloro-naphthyl moiety possesses a larger dipole moment,thereby enhancing the interaction between chloro-naphthyl end-capped PM6 with the small molecule acceptor,L8-BO,significantly reducing theπ-πstacking distances between molecules and enhancing charge-carrier mobilities.Devices based on PM6-Cl:L8-BO exhibited appropriate phase separation,optimal molecular orientation,and minimal charge recombination.Consequently,the PM6-Cl:L8-BO-based device achieved an outstanding power conversion efficiency of 18.07%,with simultaneous enhancements in short-circuit current density(J_(SC))and fill factor(FF).This was much higher than those of PM6-F:L8-BO-based(17.60%)and PM6-H:L8-BO-based(16.87%)devices.These results demonstrated that the modulation of end-capped atoms in PM6 could significantly improve the photovoltaic performance of organic solar cells and provide guidance for the design and synthesis of highperformance polymers.
文摘Ionomer impregnation represents a milestone in the evolution of polymer electrolyte fuel cell （PEFC） catalyst layers. Ionomer acts as the binder, facilitates proton transport, and thereby drastically improves catalyst utilization and effectiveness. However, advanced morpho- logical and functional characterizations have revealed that up to 60% of Pt nanoparticles can be trapped in the micropores of carbon support particles. Ionomer clusters and oxygen molecules can hardly enter into micropores, leading to low Pt utilization and effectiveness. Moreover, the ionomer thin-films covering Pt nanoparticles can cause significant mass transport loss especially at high current densities. Ionomer-free ultra-thin catalyst layers （UTCLs） emerge as a promising alternative to reduce Pt loading by improving catalyst utilization and effectiveness, while theoretical issues such as the proton conduction mechan- ism remain puzzling and practical issues such as the rather narrow operation window remain unsettled. At present, the development of PEFC catalyst layer has come to a crossroads： staying ionomer-impregnated or going iono- mer-free. It is always beneficial to look back into the past when coming to a crossroads. This paper addresses the characterization and modeling of both the conventional ionomer-impregnated catalyst layer and the emerging ionomer-free UTCLs, featuring advances in characterizing microscale distributions of Pt particles, ionomer, support particles and unraveling their interactions; advances in fundamental understandings of proton conduction and flooding behaviors in ionomer-free UTCLs; advances in modeling of conventional catalyst layers and especially UTCLs; and discussions on high-impact research topics in characterizing and modeling of catalyst layers.
