The impact of stress and interface composition on the study of CsF/CsPbX3 inorganic perovskite heterojunctions

Abstract

In this paper, using first-principles calculations, we have shown that the electronic properties of the CsF/CsPbX3 (X = Cl, Br, I) heterojunctions can be effectively modulated by applying in-plane strain. The CsF/CsPbX3 heterojunction structures exhibit low-lattice mismatch ratios (Cl-Br-I, 3.6 %-1.8 %-4.3 %). Pb²⁺ and F⁻ attract each other to form PbF2, Cs+ and X−attract each other to form CsX. The binding energies are -0.578, -0.406, and -0.723 eV (Cl, Br and I), respectively, indicating that CsF/CsPbI3 exhibits the superior stability. Three heterojunctions are direct band gap semiconductors and the band gaps increase compared to inorganic perovskites (ΔEg:CsPbCl3CsPbBr3CsPbI3, 0.640–0.652–0.601 eV). The partial density of states indicates that the band gap contribution is related the [PbX3]− octahedron and F−. It is evident from the absorption spectra that the interaction of the CsF/CsPbX3 heterojunctions produces a blue shift. By combining multiple layers of CsF and CsPbX3, an overall broad spectral response can be achieved. The optical parameters of CsF/CsPbX3 are consistent with the changes in the band gap. This study demonstrates that CsF can enhance the stability adjust of the spectral response range of inorganic perovskite sensors, and improve the optical absorption performance. The study provides valuable theoretical guidance for the research of high-performance CsF/CsPbX3 heterojunction sensors.