Molecularly tailored perovskite/poly(3-hexylthiophene) interfaces for high-performance solar cells

Abstract

Dopant-free poly(3-hexylthiophene) (P3HT) hole transport materials (HTMs) have been acknowledged for their significant potential in enhancing the stability of perovskite solar cells (PSCs). However, the severe recombination loss occurring at perovskite/P3HT interfaces exhibits a tremendous impediment to their photovoltaic efficiency. Herein, we develop a general molecular engineering strategy using tailorable phosphine ligands to modulate the perovskite/P3HT interface for effectively alleviating the recombination loss and maximizing the device voltage. Theoretical and experimental results reveal that the phosphine ligand with balanced electronic and steric properties could establish a strong binding interaction with perovskite, which not only passivates deep-level antisite defects for suppressing energy loss but also optimizes the energy level alignment to facilitate carrier transfer. This approach is applicable to the perovskites with various bandgaps, such as 1.53 eV (CsFAPbI₃), 1.7 eV (CsPbI₃), and 1.9 eV (CsPbI₂Br), delivering top-tier efficiencies of 25.08% (certified 24.54%), 21.42%, and 18.39%, respectively. Benefiting from the improved interface and dopant-free HTMs, these PSCs exhibit outstanding stability under accelerated aging conditions.