Electron‐Phonon Interactions Facilitating Large Polaron‐Related Charge‐Carrier Dynamics for Efficient Perovskite Nanocrystal Solar Cells

ABSTRACT Recent years have witnessed the accelerated development of optoelectronic devices based on lead halide perovskites‐based nanocrystal (NC) films. Yet, to date we have limited knowledge on how the NC's surface affects the long‐range charge‐carrier dynamics in these films. In this work, we exchange the native ligands on the surface of CsPbI 3 NCs with three different thiopheneammonium‐based ligands. Among them, the custom‐synthesized 2‐thiophenepropenammonium iodide (TPAI) is found to significantly affect the collective phonon states in the NC films, and specifically decrease the strength of the carrier‐lattice interactions (by ∼half when compared to the other thiopheneammonium‐based ligands). This in turns promoted the formation of large polarons, which are beneficial for charge‐carrier dynamics. By employing the TPAI‐optimized CsPbI 3 NC films to fabricate solar cells, a champion efficiency of 16.67% is achieved. Additionally, TPAI fostered excellent device stability in ambient air (91.8 ± 0.4% of the initial efficiency after 1100 h) and under light soaking conditions (84.6% after 1000 h). This work provides a rationale connecting the type of surface ligand molecules with the strength of carrier‐lattice interactions, thus proving additional insights into mechanisms governing charge‐carrier dynamics in NC film‐based devices.