Tailorable PC BM Isomers: Using the Most Prevalent Electron Acceptor to Obtain High-Performance Polymer Solar Cells.

Despite being widely used as electron acceptor in polymer solar cells, commercially available PC BM (phenyl-C -butyric acid methyl ester) usually has a "random" composition of mixed regioisomers or stereoisomers. Here PC BM has been isolated into three typical isomers, α-, β - and β -PC BM, to establish the isomer-dependent photovoltaic performance on changing the ternary composition of α-, β - and β -PC BM. Mixing the isomers in a ratio of α/β /β =8:1:1 resulted in the best power conversion efficiency (PCE) of 7.