Enhancing\nExtraction and Suppressing Cooling of Hot\nElectrons in Lead Halide Perovskites by Dipolar Surface Passivation

Slowing hot carrier\n(HC) cooling and improving HC extraction are\nconsidered two pivotal factors for enhancing power conversion efficiency\nin emerging HC photovoltaic applications of perovskites and other\nmaterials. Employing ab initio quantum dynamics simulations, we demonstrate\nthe simultaneous slow cooling and efficient extraction of hot electrons\nat the C<sub>60</sub>/CsPbI<sub>3</sub> interface through dipolar\nsurface passivation with phenethylammonium and 4-fluorophenethylammonium\nligands. The passivation effectively suppresses I–Pb lattice\nvibrations, weakens the hot electron–phonon interaction in\nCsPbI<sub>3</sub>, and thus slows down the HC cooling. At the same\ntime, the dipolar surface passivation elevates the LUMO + 1 state\nin C<sub>60</sub> and reduces the energy gap for HC extraction. Concurrently,\nhigher-frequency vibrations of the dipolar layer enhance the coupling\nbetween C<sub>60</sub> and CsPbI<sub>3</sub>, promoting efficient\nHC extraction further. These phenomena are intensified with increased\npolarity of the dipolar layer. Furthermore, we find that dipolar passivation\nhas the opposite influence on cold electron collection at the band\nedge, underscoring the fact that the observed improvement in photovoltaic\nperformance stems preferentially from the effective utilization of\nHCs rather than cold electrons. The work provides a new strategy for\nachieving high-performance HC perovskite solar cells.