Peripheral substituent regulation of bias structured azulene-based hole transport materials for perovskite solar cells

Abstract

Hole transport materials (HTMs) have an important impact on the improvement of perovskite solar cell (PSC) performance. So far, HTMs with symmetrical and unbiased molecular structures have been extensively studied. Azulene, which is composed of a seven-membered ring and a five-membered ring, has shown nice potential in organic field-effect transistors and organic photovoltaic cells. In this research, we synthesized four bias structured HTMs (Azu-diT, Azu-diF, Azu-2T6F and Azu-2F6T) based on 2,6-substituted azulene. Among them, the more bias structured HTMs showed better electronic properties, and peripheral substitution on the 6-position of azulene had a greater influence on the solubility and film formation property. After being applied in PSCs, a power conversion efficiency (PCE) up to 16.16% was obtained by Azu-2T6F. These results demonstrate the potential of azulene derivatives as a hole transport material and the impact of biased peripheral regulation.