Recent research progress in perovskite-based type-II heterojunction photodetectors and solar cells

Metal halide perovskites have become promising semiconductor materials for next-generation optoelectronic devices, showing excellent performance. However, single-component perovskites still suffer from rapid carrier recombination and limited spectral response, which restrict device performance. Therefore, considerable research efforts have been devoted to constructing Type-II heterojunctions with staggered band alignment to achieve efficient charge separation and suppressed recombination. This review summarizes the fundamental properties of Type-II perovskite heterojunctions, their roles and trade-offs in optoelectronic devices, as well as the regulation and optimization of device performance and stability via multiple means including compositional engineering, dimensional design, interface passivation and strain engineering. This review establishes a framework linking mechanism, performance, and application that correlates band alignment, interfacial defects, carrier dynamics, and device architecture with key performance metrics, and compares the device-dependent roles and trade-offs of Type-II band alignment. The field has made great progress in understanding and engineering Type-II perovskite heterojunctions and has improved device performance beyond expectations. Nonetheless, there are still ample opportunities to further improve efficiency and long-term stability, either by optimizing band alignment or by mitigating interfacial defects and ion migration.