Supersaturation- and external force-engineered high-quality 2D CsCu2I3 single-crystalline film for heterogeneous integration in photodetectors

Heterogeneous integration of various crystalline materials in electronic and optoelectronic devices have fueled the development of two-dimensional (2D) perovskite single-crystalline (SC) film. However, it is still challenging to synthesize 2D CsCu 2 I 3 SC film due to the uncontrolled nuclei/growth. In the work, the bottleneck for the synthesis of 2D CsCu 2 I 3 SC film can be well tackled by the solution supersaturation and external pressure for the first time, meanwhile, the morphological transformation of CsCu 2 I 3 from dendritic crystal to 2D film are firstly achieved through controlling nucleation driving force. The heterogeneous integration of 2D CsCu 2 I 3 SCs film on various substrates was demonstrated, a self-powered GaN-CsCu 2 I 3 SC film photodetector exhibits high rectification ratio of 1250 (±1 V) with improved responsivity of 460 mA W −1 and EQE of 163 %, which outperforms most reported 2D lead-free halide perovskite film photodetectors. Furthermore, theoretical computational calculation was employed to investigate their crystal structure and electronic distribution, evidencing that 2D CsCu 2 I 3 SC film could facilitate the separation of photo-induced carriers. The study not only shows an in-depth mechanism for perovskite growth, but also advances the development of 2D copper-based perovskite film and hetero-integration, laying the groundwork for future commercial optoelectronics.