Effect of thiophene chain lengths on the optical and hole transport properties for perovskite solar cells

We report the effect of the thiophene chain extension on optical property and hole mobility of a set of 3,4,5-tetra[4,4′-bis(methoxyphenyl)aminophen-4″-yl]-thiophene (H111) derivatives (H112, H113, H114, and H115) by using first-principles calculations combined with Marcus theory. Our results show that extension of the thiophene chain not only brings a red-shift on the absorption spectrum, but also enhances the intensity of the largest absorption. Moreover, with the increase of the thiophene number, the reorganization energy between the neutral and cation states gradually reduces, leading to a continuous decrease in exciton binding energy from H111 to H115. Importantly, we reveal that sulfur (S) atoms play dominant roles in hole transfer, and the corresponding S»S distances in stacked dimers are inversely proportional to hole mobility. Compared with H111 and H112, H114 and H115 exhibit evidently large hole mobility thus are recommended as potential hole transport materials for perovskite solar cells.