Inclusion of triphenylamine unit in dopant-free hole transport material for enhanced interfacial interaction in perovskite photovoltaics

Dopant-free hole transport material (HTM) has been recognized as an essential material for achieving efficient and stable perovskite photovoltaics (PPVs). Currently, conjugated polymer has emerged as a promising dopantfree HTM; however, its insufficient interaction with perovskite absorbers limits an efficient interfacial passivation and charge extraction when employed in PPVs. In this study, we developed a high-performance dopant-free HTM by the partial substitution of a conjugated polymer with triphenylamine unit. The analysis of the performance of the HTM revealed that the modification of the polymer HTM using triphenylamine unit enhanced its interaction with perovskite and its passivation ability. Furthermore, an increase in the number of face-on orientated crystallites after the triphenylamine substitution enhanced the charge transport ability of the polymer HTM. Consequently, the PPVs fabricated using the triphenylamine-substituted polymer HTM exhibited a high efficiency of 20.4% and an enhanced long-term stability compared to the devices fabricated using a control polymer without triphenylamine-substitution (15.8%).