Effect of double bond conjugation on hole mobility of thiophene-based hole transport materials in perovskite solar cells

Abstract

It is of great significance to fully explore the relationship between π-bridge size and intermolecular packing for improving the hole mobility of hole transport materials in perovskite solar cells. We performed the density functional theory (DFT) computations of a series of Z26 derivatives (Z26-2, Z26-3, and Z26-4) and investigated the effect of the size of π-bridge and intermolecular packing on hole mobility of hole transport materials. The calculated results show that Z26-2 (7.7 × 10−4 cm2 V−1 s−1) and Z26-3 (1.3 × 10−3 cm2 V−1 s−1) have larger hole mobility than Z26 (5.60 × 10−4 cm2 V−1 s−1) due to their appropriate conjugated length leading to effective face to face packing. The smallest hole mobility of Z26-4 (4.20 × 10−5 cm2 V−1 s−1) is attributed to its overlong conjugation with four double bonds on each side, which produces a long centroid-to-centroid distance and small electronic coupling. The present theoretical study on the relationship between the size of π-bridge and intermolecular packing provides insight for the future design of thiophene-based hole transport materials.