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Due to the vigorous development of polymerized small-molecule acceptors (PSMAs), all-polymer solar cells (all-PSCs) have made tremendous advancement recently. However, their power conversion efficiencies (PCEs) are still restricted by the lack of PSMAs with desirable optoelectronic properties, especially the ability to capture the near-infrared photons. To resolve this, two near-infrared absorbing PSMAs, namely PY2Se-F and PY2Se-Cl, with a selenophene-fused core and halogenated end-group are developed. Combining the synergistic effects of selenium and fluorine (F)/chlorine (Cl) substitutions in broadening absorption and enhancing intermolecular interactions, PY2Se-F and PY2Se-Cl show significantly red-shifted absorption (30-40 nm) and reasonably deep-shifted lowest unoccupied molecular orbital (LUMO) levels compared with the pristine PY2S-H and fluorinated PY2S-F. When replacing F with Cl on the end-group, the PY2Se-Cl shows a better blend morphology with polymer donor PM6, compared with the PY2Se-F-based one, leading to better charge transport. As a result, the PM6:PY2Se-Cl-based all-PSCs achieve an impressive PCE of 16.1% with both high short-circuit current density (J(sc)) of 24.5 mA cm(-2) and fill factor (FF) of 0.743, which are among the highest values in the reported binary all-PSCs so far. Notably, this is the first example of chlorinated end-group derived PSMAs. Combining with the low-cost merit of chlorination, PY2Se-Cl shows great potential in the practical applications of efficient all-PSCs.

Due to the vigorous development of polymerized small-molecule acceptors (PSMAs), all-polymer solar cells (all-PSCs) have made tremendous advancement recently. However, their power conversion efficiencies (PCEs) are still restricted by the lack of PSMAs with desirable optoelectronic properties, especially the ability to capture the near-infrared photons. To resolve this, two near-infrared absorbing PSMAs, namely PY2Se-F and PY2Se-Cl, with a selenophene-fused core and halogenated end-group are developed. Combining the synergistic effects of selenium and fluorine (F)/chlorine (Cl) substitutions in broadening absorption and enhancing intermolecular interactions, PY2Se-F and PY2Se-Cl show significantly red-shifted absorption (30-40 nm) and reasonably deep-shifted lowest unoccupied molecular orbital (LUMO) levels compared with the pristine PY2S-H and fluorinated PY2S-F. When replacing F with Cl on the end-group, the PY2Se-Cl shows a better blend morphology with polymer donor PM6, compared with the PY2Se-F-based one, leading to better charge transport. As a result, the PM6:PY2Se-Cl-based all-PSCs achieve an impressive PCE of 16.1% with both high short-circuit current density (J(sc)) of 24.5 mA cm(-2) and fill factor (FF) of 0.743, which are among the highest values in the reported binary all-PSCs so far. Notably, this is the first example of chlorinated end-group derived PSMAs. Combining with the low-cost merit of chlorination, PY2Se-Cl shows great potential in the practical applications of efficient all-PSCs.

Due to the vigorous development of polymerized small-molecule acceptors (PSMAs), all-polymer solar cells (all-PSCs) have made tremendous advancement recently. However, their power conversion efficiencies (PCEs) are still restricted by the lack of PSMAs with desirable optoelectronic properties, especially the ability to capture the near-infrared photons. To resolve this, two near-infrared absorbing PSMAs, namely PY2Se-F and PY2Se-Cl, with a selenophene-fused core and halogenated end-group are developed. Combining the synergistic effects of selenium and fluorine (F)/chlorine (Cl) substitutions in broadening absorption and enhancing intermolecular interactions, PY2Se-F and PY2Se-Cl show significantly red-shifted absorption (30-40 nm) and reasonably deep-shifted lowest unoccupied molecular orbital (LUMO) levels compared with the pristine PY2S-H and fluorinated PY2S-F. When replacing F with Cl on the end-group, the PY2Se-Cl shows a better blend morphology with polymer donor PM6, compared with the PY2Se-F-based one, leading to better charge transport. As a result, the PM6:PY2Se-Cl-based all-PSCs achieve an impressive PCE of 16.1% with both high short-circuit current density (J(sc)) of 24.5 mA cm(-2) and fill factor (FF) of 0.743, which are among the highest values in the reported binary all-PSCs so far. Notably, this is the first example of chlorinated end-group derived PSMAs. Combining with the low-cost merit of chlorination, PY2Se-Cl shows great potential in the practical applications of efficient all-PSCs.

Y Despite the significant progresses made in all-polymer solar cells (all-PSCs) recently, the relatively low short-circuit current density (J(sc)) and large energy loss are still quite difficult to overcome for further development. To address these challenges, we developed a new class of narrow-bandgap polymer acceptors incorporating a benzotriazole (BTz)-core fused-ring segment, named the PZT series. Compared to the commonly used benzothiadiazole (BT)-containing polymer PYT, the less electron-deficient BTz renders PZT derivatives with significantly red-shifted optical absorption and up-shifted energy levels, leading to simultaneously improved J(sc) and open-circuit voltage in the resultant all-PSCs. More importantly, a regioregular PZT (PZT-gamma) has been developed to achieve higher regiospecificity for avoiding the formation of isomers during polymerization. Benefiting from the more extended absorption, better backbone ordering, and more optimal blend morphology with donor component, PZT-gamma-based all-PSCs exhibit a record-high power conversion efficiency of 15.8% with a greatly enhanced J(sc) of 24.7 mA/cm(2) and a low energy loss of 0.51 eV., Funding Agencies|APRC Grants of the City University of Hong Kong [9380086]; Innovation and Technology Bureau [ITS/497/18FP, GHP/021/18SZ]; Guangdong-Hong Kong-Macao joint laboratory of optoelectronic and magnetic materials [2019B121205002]; Research Grants Council of Hong KongHong Kong Research Grants Council [C5037-18G]; Guangdong Major Project of Basic and Applied Basic Research [2019B030302007]; Office of Naval ResearchOffice of Naval Research [N00014-20-1-2191]; Hong Kong Scholars Program [XJ2019-026]; National Natural Science Foundation of ChinaNational Natural Science Foundation of China (NSFC) [21905225]; Science and Technology Program of Shanxi Province [2019JQ-244]; National Research Foundation (NRF) of KoreaNational Research Foundation of Korea [NRF2016M1A2A2940911, 2019R1A6A1A11044070]; Stiftelsen for Strategisk Forskning through the Future Research Leader program [FFL18-0322]

In this work, a range of nonfullerene organic solar cells comprising two perylene diimide (PDI)-based small molecule acceptors in combination with four representative polymer donors have been investigated and compared. In addition to significant differences in the power conversion efficiency, the energy losses of photovoltaic devices vary widely for these two PDI-based acceptors when paired with different donors. The sensitive Fourier-transform photocurrent spectroscopy (FTPS) and electroluminescence (EL) measurements have been performed to quantify their respective energetic offsets (Delta(Eoffiet)) and energy losses, with the aim of understanding the distinct energy losses in the studied organic blends. By comparing these results, we find that with decreasing Delta(Eoffset), recombination loss due to the charge-transfer state absorption A both nonradiative recombination loss and radiative are suppressed; as a result, the total energy loss is decreased. These observations offer a deep understanding of how the energetic offset affects the energy losses from the viewpoint of the Shockey-Queisser limit., Funding Agencies|National Natural Science Foundation of China (NSFC) [21734009, 21734001, 21672221]; NSFC-DFG [21661132006, TRR61]; Chinese Academy of Sciences [XDB12010100]; Swedish Energy Agency Energimyndigheten [2016-010174]; Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University [2009-00971]; China Scholarship Council

In this work, a range of nonfullerene organic solar cells comprising two perylene diimide (PDI)-based small molecule acceptors in combination with four representative polymer donors have been investigated and compared. In addition to significant differences in the power conversion efficiency, the energy losses of photovoltaic devices vary widely for these two PDI-based acceptors when paired with different donors. The sensitive Fourier-transform photocurrent spectroscopy (FTPS) and electroluminescence (EL) measurements have been performed to quantify their respective energetic offsets (Delta(Eoffiet)) and energy losses, with the aim of understanding the distinct energy losses in the studied organic blends. By comparing these results, we find that with decreasing Delta(Eoffset), recombination loss due to the charge-transfer state absorption A both nonradiative recombination loss and radiative are suppressed; as a result, the total energy loss is decreased. These observations offer a deep understanding of how the energetic offset affects the energy losses from the viewpoint of the Shockey-Queisser limit., Funding Agencies|National Natural Science Foundation of China (NSFC) [21734009, 21734001, 21672221]; NSFC-DFG [21661132006, TRR61]; Chinese Academy of Sciences [XDB12010100]; Swedish Energy Agency Energimyndigheten [2016-010174]; Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University [2009-00971]; China Scholarship Council

In this work, a range of nonfullerene organic solar cells comprising two perylene diimide (PDI)-based small molecule acceptors in combination with four representative polymer donors have been investigated and compared. In addition to significant differences in the power conversion efficiency, the energy losses of photovoltaic devices vary widely for these two PDI-based acceptors when paired with different donors. The sensitive Fourier-transform photocurrent spectroscopy (FTPS) and electroluminescence (EL) measurements have been performed to quantify their respective energetic offsets (Delta(Eoffiet)) and energy losses, with the aim of understanding the distinct energy losses in the studied organic blends. By comparing these results, we find that with decreasing Delta(Eoffset), recombination loss due to the charge-transfer state absorption A both nonradiative recombination loss and radiative are suppressed; as a result, the total energy loss is decreased. These observations offer a deep understanding of how the energetic offset affects the energy losses from the viewpoint of the Shockey-Queisser limit., Funding Agencies|National Natural Science Foundation of China (NSFC) [21734009, 21734001, 21672221]; NSFC-DFG [21661132006, TRR61]; Chinese Academy of Sciences [XDB12010100]; Swedish Energy Agency Energimyndigheten [2016-010174]; Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University [2009-00971]; China Scholarship Council

In this work, a range of nonfullerene organic solar cells comprising two perylene diimide (PDI)-based small molecule acceptors in combination with four representative polymer donors have been investigated and compared. In addition to significant differences in the power conversion efficiency, the energy losses of photovoltaic devices vary widely for these two PDI-based acceptors when paired with different donors. The sensitive Fourier-transform photocurrent spectroscopy (FTPS) and electroluminescence (EL) measurements have been performed to quantify their respective energetic offsets (Delta(Eoffiet)) and energy losses, with the aim of understanding the distinct energy losses in the studied organic blends. By comparing these results, we find that with decreasing Delta(Eoffset), recombination loss due to the charge-transfer state absorption A both nonradiative recombination loss and radiative are suppressed; as a result, the total energy loss is decreased. These observations offer a deep understanding of how the energetic offset affects the energy losses from the viewpoint of the Shockey-Queisser limit., Funding Agencies|National Natural Science Foundation of China (NSFC) [21734009, 21734001, 21672221]; NSFC-DFG [21661132006, TRR61]; Chinese Academy of Sciences [XDB12010100]; Swedish Energy Agency Energimyndigheten [2016-010174]; Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University [2009-00971]; China Scholarship Council

In this work, a range of nonfullerene organic solar cells comprising two perylene diimide (PDI)-based small molecule acceptors in combination with four representative polymer donors have been investigated and compared. In addition to significant differences in the power conversion efficiency, the energy losses of photovoltaic devices vary widely for these two PDI-based acceptors when paired with different donors. The sensitive Fourier-transform photocurrent spectroscopy (FTPS) and electroluminescence (EL) measurements have been performed to quantify their respective energetic offsets (Delta(Eoffiet)) and energy losses, with the aim of understanding the distinct energy losses in the studied organic blends. By comparing these results, we find that with decreasing Delta(Eoffset), recombination loss due to the charge-transfer state absorption A both nonradiative recombination loss and radiative are suppressed; as a result, the total energy loss is decreased. These observations offer a deep understanding of how the energetic offset affects the energy losses from the viewpoint of the Shockey-Queisser limit., Funding Agencies|National Natural Science Foundation of China (NSFC) [21734009, 21734001, 21672221]; NSFC-DFG [21661132006, TRR61]; Chinese Academy of Sciences [XDB12010100]; Swedish Energy Agency Energimyndigheten [2016-010174]; Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University [2009-00971]; China Scholarship Council