A Terminally Tetrafluorinated Nonfullerene Acceptor for Well‐Performing Alloy Ternary Solar Cells

• DOI: 10.1002/adfm.201805872
• Publication Date: 2019-01-31T07:42:36Z
• Authors: Ruizhi Lv; Dong Chen; Xunfan Liao; Lie Chen; Yiwang Chen
• Keywords: Acceptor; HOMO/LUMO; Methylene

Abstract Fabricating ternary solar cells is a pivotal strategy to improve the power conversion efficiencies (PCEs) of organic photovoltaic devices. However, it still challenge simultaneously performance parameters Therefore, third ingredient in blends should be precisely designed or selected. Herein, new medium‐bandgap small‐molecule acceptor, namely, 3,9‐bis(2‐methylene‐(3‐(1‐(3,5‐dimethylphenyl)‐1cyanomethylene)indanone))‐5,5,11,11‐tetrakis‐(4‐hexylphenyl)dithieno[2,3‐d:2′,3′‐d′]‐sindaceno[1,2‐b:5,6‐b′]dithiophene (ITIF), synthesized by end‐capping with fluorinated, asymmetric terminal group, (Z)‐2‐(3,5‐difluorophenyl)‐2‐(3‐oxo‐2,3‐dihydro‐1H‐inden‐1‐ylidene) acetonitrile. Replacing CN substituent 3,5‐difluorophenyl obviously up‐shifts lowest unoccupied molecular orbital (LUMO) level ITIF −3.78 eV, enlarges bandgap 1.82 and improves absorption coefficient ≈50% higher than that 3,9‐bis(2‐methylene‐(3‐(1,1‐dicyanomethylene)indanone))‐5,5,11,11‐tetrakis‐(4‐hexylphenyl)dithieno[2,3‐d:2′,3′‐d′]‐sindaceno[1,2‐b:5,6‐b′]dithiophene (ITIC). Due similar structures, ITIC can combine as an alloyed which makes convenient tune morphology optical electrochemical properties blends. The enhanced rapid fluorescence resonance energy transfer from remarkably blend film, hence compensating for external quantum efficiency (EQE) curves. When introduced into based on poly[(2,6‐(4,8‐bis(5‐(2‐ethylhexyl)thiophen‐2‐yl)‐benzo[1,2‐b:4,5‐b′]dithiophene))‐alt‐(5,5‐(1′,3′‐di‐2‐thienyl‐5′,7′‐bis(2‐ethylhexyl)benzo[1′,2′‐c:4′,5′‐c′]dithiophene‐4,8‐dione)] (PBDB‐T):ITIF:ITIC blends, PCEs devices are increased 9.2% 10.5%, short‐circuit currents, open‐circuit voltages, fill factors improved.