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

Abstract This paper investigates the PbS/PbSe/CsPbI 3 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/CsPbI 3 and PbS/CsPbI 3 all possess relatively low lattice mismatch rates (2.3%, 2.4% and 4.6%) and similar octahedral structures. The PbS/CsPbI 3 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/CsPbI 3 -PbS/CsPbI 3 , 0.632–0.856–0.523 eV). The spectral comparison shows that PbS/PbSe/CsPbI 3 > PbSe/CsPbI 3 > CsPbI 3 , indicating that PbS/PbSe/CsPbI 3 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/CsPbI 3 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/CsPbI 3 heterojunction as visible-near infrared optoelectronic materials.