Device Physics and Design Principles of 1D/3D Heterojunction Perovskite Solar Cells

Introducing a one‐dimensional (1D) perovskite structure onto the surface of three‐dimensional (3D) perovskites can effectively improve device performance; however, experimental studies have long simplified the underlying mechanism to interface passivation and physical blocking of ion migration. In this work, by constructing a coupled multi‐physics model for both pure 3D and 1D/3D heterojunctions, we find that the 1D layer functions not merely as a passivation and blocking layer. Instead, through optimized band alignment, it modulates the carrier concentration distribution, inducing a strong built‐in electric field that drives carrier separation and transport. This built‐in field also regulates ion distribution, effectively suppressing the hysteresis effect. Furthermore, the 1D structure significantly broadens the material selection range for both the hole transport layer and the 3D perovskite. Ultimately, the device achieves a theoretical efficiency of 28.8%, providing theoretical guidance for the design of high‐efficiency 1D/3D heterojunction perovskite solar cells.