High-Efficiency Organic Solar Cells With Solution Processable Non-Fullerene Acceptor as an Interlayer

Interlayers and interface engineering plays a pivotal role in achieving efficient charge extraction necessary for realizing high power conversion efficiency (PCE) in bulk heterojunction organic solar cells. In this study, we report a novel strategy of combining advantages of both fullerene derivative and non-fullerene acceptor materials by employing solution processable non-fullerene acceptor 3,9-bis(2-methylene-(3-(1,1-dicyanomethylene)-indan-one))-5,5,11,11-tetrakis(4-hexylphenyl)-dithieno[2,3-d:2',3'-d']-s-indaceno[1,2-b:5,6-b']dithiophene (ITIC) to modify the interface between ZnO-based electron transport layer and poly[4,8-bis (5-(2-ethylhexyl)thiophen-2-yl) benzo [1,2-b;4,5-b'] dithiophene-2,6-diyl-alt-(4-(2-ethylhexyl)-3-fluorothieno[3,4-b]thiophene-)-2-carb-oxyhtte-2-6-diyl)] (PTB7-Th): phenyl-C-71-butyric acid methyl ester-based photoactive layer. An improvement in PCE from similar to 7.5% to similar to 9% has been achieved for the devices with ITIC modified interlayer. Time resolved photoluminescence (PL) via time correlated single photon counting and photo-electrochemical impedance spectroscopy (photo-EIS) measurements were carried out to investigate the causes for improved PCE for the devices with ITIC modified interlayer.