Porphyrins with di-alkoxy-thiophene side chains for organic solar cells

Abstract

The crystallinity of the electron donors and their compatibility with the electron acceptors play important roles for the performance of bulk-heterojunction organic solar cells. Considering that large electronegative atoms such as O and S atoms are often introduced in the active materials to enhance the intermolecular interactions and poly(3,4-ethylenedioxythiophene) (PEDOT) is a highly conductive polymer, here in, we introduce dimethoxythiophene (DMOT) and ethylene dioxyl-thiophene (EDOT) side chains at two of the meso positions of a porphyrin core to synthesize two small molecular donors ZnP-DMOT and ZnP-EDOT, and the PCEs of 9.63% and 9.06%, respectively, are achieved for the OSCs with PC61BM as the acceptor. These PCEs are very close to state-of-the-art among fullerene-based OSCs. In addition, when non-fullerene acceptor 6TIC was employed, the ZnP-DMOT and the ZnP-EDOT binary devices show PCEs of 11.55% and 10.86%, respectively. Experimental results show that di-alkoxy groups improve not only the crystallinity of the porphyrins but also the compatibility with PC61BM and 6TIC. Furthermore, the introduction of PC61BM as the third component into 6TIC based binary layers significantly improves the electron mobility and the balance of hole and electron transport. As results, the ternary ZnP-DMOT:6TIC:PC61BM and ZnP-EDOT:6TIC:PC61BM devices achieve PCEs of 13.32% and 12.96%, respectively.