Heterocyclic Functionalized Donor-Acceptor Hole-Transporting Materials for Inverted Perovskite Solar Cells

Hole transport materials (HTMs) with appropriate energylevelsand comprehensive passivation effects help to obtain highly efficientand stable perovskite solar cells (PSCs). Electron-deficient character-inducedHTMs can generate varying energy level alignments near the HTM/perovskiteinterface. Herein, we report the synthesis and investigation of twonew dipolar HTMs, WWC103 and WWC105, basedon 2-(1,1-dicyanomethylene)rhodamine and 4-cynophenylacetonitrileacceptors, enabling high-efficiency mixed-cation mixed-halide perovskitesolar cells. Apart from having different acceptors, these HTMs arebuilt on a heterocyclic frame, which can provide passivation effectsand improve the morphology of the perovskite layer. As a result, thesedopant-free HTM-based solar cells show a high open-circuit voltageand good power conversion efficiency. Among both, the solar cell basedon the HTM with 2-(1,1-dicyanomethylene)rhodamine exhibits a highopen-circuit voltage of 1.09 V with a champion power conversion efficiencyof over 20.51%. The improved performance of WWC103 over WWC105 (19.74%) is attributed to the new acceptor, which,in addition to providing good energy-level alignments and hole mobility,also holds the ability to passivate the defects. The findings suggesta new acceptor unit for constructing dopant-free HTMs for efficientPSCs.