Quantitatively Characterized Crystallization Effect on Recombination Energy Loss in Non-Fullerene Organic Solar Cells

Recombination energy loss is the main impediment on improving the power conversion efficiency of organic solar cells (OSCs). The pernicious effect is usually induced by two dynamics, that is, the geminate recombination of nascent charge pairs soon after the exciton dissociation and nongeminate recombination of separated charges during their transportation. Both hinder achieving high open-circuit voltage (VOC). Here, we comprehensively investigated the relationship between crystallization and molecular recombination in a non-fullerene system of poly[(2,6-(4,8-bis(5-(2-ethylhexyl)thiophen-2-yl)benzo[1,2-b:4,5-b′]dithiophene)-co-(1,3-di(5-thiophene-2-yl)-5,7-bis(2-ethylhexyl)-benzo[1,2-c:4,5-c′]dithiophene-4,8-dione))] (PBDB-T):((5Z,50Z)-5,50-(((4,4,9,9-tetraoctyl-4,9-dihydro-s-indaceno[1,2-b:5,6-b0]dithiophene-2,7-diyl)bis(benzo[c][1,2,5]thiadia-zole-7,4-diyl))bis(methanylylidene))bis(3-ethyl-2-thioxothiazolidin-4-one)) (O-IDTBR). Based on a quantitative characterization of crystallinity, it was found that ...