Ammonium Salt Assisted Crystallization for High Performance Two- Dimensional Lead-Free Perovskite Photodetector

Two-dimensional Ruddlesden-Popper lead-free perovskites show promising prospects for application in optoelectronic devices due to their tunable optoelectronic properties and environmental friendliness. However, their carrier mobility and stability are limited by the crystal morphology and lattice direction, which hinder the improvement of their optoelectronic device performance. Here, we introduce a convenient ammonium assistance method to improve the crystallinity and lattice orientation of 2D perovskite films, through which carrier mobility and stability of 2D perovskites can be significantly improved. Oriented crystals, increased grain size, and improved crystal quality contribute to the high performance of lateral photodetectors. The champion device exhibits high Responsivity, External Quantum Efficiency, and Detectivity (938 A/W, 34714%, and 3.70 x 1014 Jones, respectively), as well as outstanding stability. This work reveals the potential of ammonium assistance 2D perovskite in developing high-performance and stable optoelectronic devices.