The effects of strain and interface engineering on the PbS/PbSe/CsPbI3 heterojunction

Abstract This paper investigates the PbS/PbSe/CsPbI3 heterojunction based on first-principles calculations within the framework of density functional theory and demonstrates the effects of different strains on the structural, electronic, optical properties. PbS/PbSe, PbSe/CsPbI3 and PbS/CsPbI3 all possess relatively low lattice mismatch rates (2.3%, 2.4% and 4.6%) and similar octahedral structures. The PbS/CsPbI3 heterojunction reduces carrier transfer losses between different materials. By serving as the functional layer, PbSe can alter the electron-hole recombination losses at the heterostructure interface, broaden the spectral response range, and change the electronic density around the atoms at the heterostructure interface. All three heterojunctions are direct band gap semiconductors (ΔEg: PbS/PbSe-PbSe/CsPbI3-PbS/CsPbI3, 0.632-0.856-0.523eV). The spectral comparison shows that PbS/PbSe/CsPbI3> PbSe/CsPbI3 > CsPbI3, indicating that PbS/PbSe/CsPbI3 exhibits superior stability, charge density transfer, and optical performance with a redshift in absorption spectra. Additionally, the band gap and optical properties of PbS/PbSe/CsPbI3 can be adjusted by applying strain, thereby affecting its optical absorption intensity. This work provides a theoretical foundation for improving the performance of PbS/PbSe/CsPbI3 heterojunction as visible-near infrared optoelectronic materials.