Study on Carrier Dynamics of XF2/CsPbBr3 (X = Ca, Sr, Ba) Heterojunctions

Abstract

This paper investigates the interface interaction between XF2 (X = Ca, Sr, Ba) and CsPbBr3, as well as its effects on the structural, electronic, and optical properties under strain. The XF2/CsPbBr3 are direct bandgap and II-type heterojunctions. XF2/CsPbBr3 bandgaps are 1.537 for Ca eV, 1.862 eV for Sr, and 1.503 for Ba eV, with binding energies of –1.4684, –1.5323, and –1.3755 eV, respectively, compared to CsPbBr3. The X–Br and Cs–F bonds formed through interactions between X+–Br– and Cs+–F– ensure the stability of the heterojunction. The calculation results show that the XF2/CsPbBr3 (X = Ca, Sr, Ba) heterojunction forms a stable structure driven by the electrostatic attraction between X+ and Br–. The electronic structure analysis reveals the formation of a type-II band alignment, which favors charge separation and carrier dynamics at the interface. The partial density of states indicates that [PbBr3]– and X+ are the main contributors. Optical property calculations for the heterojunction show that the interface interaction with XF2 induces a redshift.