Observation of the growth of MAPbBr3 single-crystalline thin film based on space-limited method

Organic-inorganic hybrid perovskite single-crystalline thin films (SCTFs) are promising for enhancing photoelectric device performance. One key aspect is to be able to synthesize SCTFs with large surface areas. Here, we investigated the formation of MAPbBr3 SCTF by space-limited inverse temperature crystallization method. It was found that the weak wetting substrate could reduce friction force and promote precursor ion diffusion, which enabled a continuous growth of the thin perovskite single crystal along in-plane direction. SCTFs could be obtained at the initial stage of film growth and we also observed some signs of island growth model. Pyramid-shaped islands formed first and then converged to achieve top surface growth of SCTFs. After further growth, the precursor ion concentration near the SCTF gradually decreased. The lateral crystal growth was limited by the inefficient and anisotropic long range transportation of precursor ions along the micrometer-size or nanometer-size gap, which resulted in transformation of SCTFs into polycrystalline films. Low ion diffusion in the narrow gap is still the main constraint for the preparation of the larger and thinner SCTFs.