Dopant-free benzothiadiazole bridged hole transport materials for highly stable and efficient perovskite solar cells

Abstract

D-A-D typed hole transport materials have been designed and synthesized with benzothiadiazole acceptor unit by introducing electron-withdrawing group fluorine atoms and electron-donating group alkoxy as side group. It is found that the three hole transport materials have a low-lying HOMO energy level and higher hole mobility. Furthermore, when these materials are applied in perovskite solar cell, the higher hole mobility (1.02 × 10−3 cm2 V−1 s−1) make the B3, which the fluorine atoms on core acceptor without dopants, get a power conversion efficiency of 12.1%, while spiro-OMeTAD based dopant-free perovskite solar cell only shows a 7.96% efficiency. In addition, the long-term stability of the perovskite solar cells based all the three hole transport materials improved greatly, especially B1-based cells show a favorable long-term stability, which keeps a 90% initial efficiency after 10 days at a relative humidity of 30%. Therefore, the D-A-D typed hole transport materials have a good application prospects in the field of perovskite solar cells with the incorporation of appropriate side group.