Slow Hot-Carrier Cooling Enabled by Uniformly Arranging Different-n-Value Nanoplates in Quasi-2D Perovskites through Long-Range Orbit–Orbit Interaction toward Enhancing Photovoltaic Actions

This paper reports a slow hot-carriers cooling process enabled by uniformly arranging different-n-value nanoplates in quasi-2D perovskites (PEA₂MA_n-1Pb_nI_3n+1). Here, the energetic carriers are slowly relaxing from 1.743 to 1.688 eV within the time window of 91.7 ps, shown in transient absorption (TA) dynamics. It verifies an unusual long-order electron-lattice coupling to slow down the relaxation of hot carriers, generating long-lived energetic carriers in quasi-2D perovskites. Furthermore, the long-range orbit-orbit interaction is established through orbital polarizations between excited carriers, identified by polarization-dependent photocurrent. This indicates that the long-range orbit-orbit interaction provides the necessary condition to enable the unusual long-order electron-lattice coupling, causing a slow hot-carrier cooling effect through the energy-momentum dispersion curvature within the crystalline lattice. Interestingly, with the slow hot-carrier cooling and long-range orbit-orbit interaction, the quasi-2D perovskite demonstrates superior carrier transport shown by high fill-factor values (>80%) with reduced photovoltaic loss in solar cells at all different carrier densities.