Carrier Dynamics of Facet-Dependent Heterogeneous Interfaces in High-Performance Perovskite Solar Cells

Understanding carrier dynamics at interfaces and the interplay of surface structures is critical for improving perovskite solar cells. However, the competitive impact of facet-dependent terminations and defects on carrier behavior remains unclear. Herein, carrier dynamics at all interfaces of quasi-single-crystal films with (001) and (111) preferred orientation are investigated. The carrier extraction time of the (001) top interface is the shortest (0.57 ns), followed by that of the (111) top interface (1.32 ns), while the (001)/(111) buried interfaces take longer times (3.61 and 5.87 ns), respectively. Carrier extraction at the top interface is observed to be markedly more efficient than that at the buried interface, attributed to the strong interfacial dipole and favorable band alignment induced by heterostructures involving phosphate group interactions. Moreover, the carrier extraction at the top interface of the (111) film is much lower than that of the (001) film due to severe defect-assisted nonradiative recombination. It reveals that exposed surface terminations can influence the formation energy of interfacial defects, leading to the deep-level defects. Ultimately, the (001)-oriented device with excellent carrier extraction obtains a champion power conversion efficiency of 25.26% and a T₉₀ lifetime of 400 h during maximum power point tracking.