Improving the photovoltaic performance of perovskite solar cells through the molecular design of donor–acceptor polymeric hole-transport materials

Abstract

Conjugated donor–acceptor polymers have been regarded as attractive organic semiconductors for perovskite solar cells (PSCs) as hole-transport materials (HTMs). Herein, we report the design of four novel (X-DAD)_n conjugated polymers based on alternating benzodithiophene unit (X) and thiophene-spaced benzene derivatives or pyridine (A). The variation of A building blocks has been shown to control the backbone geometry, which is crucial for achieving high charge-transport characteristics of HTMs. Particularly, introducing fluorine and methoxy-substituted blocks enabled rigid and planar backbone structure of PBPh-ff and PBPh-mm HTMs due to non-covalent intramolecular interactions. Benefiting from this merit, PBPh-ff and PBPh-mm exhibited improved hole mobilities and better hole extraction ability from MAPbI₃. As a result, employing PBPh-ff as the HTM in n–i–p PSCs provided power conversion efficiency of 19.1% with an outstanding fill factor of ca. 80%. These findings highlight the importance of molecular design and geometry control of hole-transporting polymers for efficient perovskite photovoltaic devices.