Hydrogen-Bonded Dopant-Free Hole Transport Material Enables Efficient and Stable Inverted Perovskite Solar Cells

Although many dopant-free hole transport materials (HTMs) for perovskite solar cells (PSCs) have been investigated in the literature, novel and useful molecular designs for high-performance HTMs are still needed. In this work, a hydrogen-bonding association system (NH···CO) between amide and carbonyl is introduced into the pure HTM layer. Our study demonstrates that the hydrogen-bonding association can not only significantly increase the HTM's hole transport mobility and functionalize the surface passivation to the perovskite layer, but also form Pb-N coordination bonds at the interface to promote the hole extraction while hindering the interfacial charge recombination. As a result, the PSCs based on dopantfree hydrogen-bonded HTMs can achieve a champion power conversion efficiency (PCE) of 21.62%, which is around 32% higher than the pristine PSC without the hydrogen-bonding association. Furthermore, the dopant-free hydrogen-bonded HTMs based device shows remarkable long-term light stability, retaining 87% of its original value after 500 h continuous illumination, measured at the maximum power point. This work not only provides a potential HTM with hydrogen-bonding association in PSCs, but also demonstrates that introducing hydrogen bonding into the materials is a useful and simple strategy for developing high-performance dopant-free HTMs.