Effects of ITO Substrate Hydrophobicity on Crystallization and Properties of MAPbBr₃ Single-Crystal Thin Films

Fabricating perovskite single-crystal thin films (SCTFs) in controllable manner is the major challenge for the promising potential applications in optoelectronic devices. Although modifying the substrate surface is frequently used to realize the controlled growth of perovskite SCTFs, it is still unclear how the substrate condition affects the crystallization process. In this work, we systemically investigated the effects of the surface hydrophobicity of indium tin oxide substrates on the crystallization process of MAPbBr₃ SCTFs prepared by the space-confined method. Comprehensive characterizations show that the surface morphology and crystallinity of SCTFs are improved, and the defect density is reduced when increasing the substrate hydrophobicity. The best MAPbBr₃ thin film obtained has a full width at half-height of the rocking curve of the (001) crystal plane of 0.044°. The mechanism of the substrate hydrophobicity on the crystal growth is also discussed. These results will provide guidance to the controllable growth of high-quality SCTFs for perovskite SCTF devices.