Exploring Bi³⁺ distribution characteristics of MAPbxBi1-xBr3 thin films by space-limited method

There is always a surge of interest in compositional engineering to improve the performance of organic–inorganic halide perovskite (OIHP) solar cells among research communities. However, the role of dopant in OIHPs has not been clearly clarified so far. Relying on the slow growth of spaced-limited method, crystallization details of OIPH thin films can be amplified to explore the dopant distribution behavior easily. Herein, we optimized preparation conditions of spaced-limited method, and then conducted Bi³⁺ incorporation into MAPbBr3 single-crystalline thin films (SCTFs) to further explore its impacts from another angle. PTAA-modified substrate surfaces could accelerate the diffusion of precursor ions in the slit, which facilitated to obtain large area OIPH thin films. After Bi³⁺ incorporation, it's easy to find that Bi³⁺ could gradually aggregate on the top surface of MAPbxBi1-xBr3 thin films to form a layer of brown materials (MAPbBr3 crystal grains containing high Bi³⁺ content). As Bi³⁺ concentration increased in precursor solution, Bi³⁺-based perovskite (MA3Bi2Br9) would finally separate. Bi³⁺ distribution behavior and growth mechanism of MAPbxBi1-xBr3 thin films can give more enlightenment for understanding the role of dopant ions in OIHPs for applications in modern electronics.
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