Invalidity of Band-Gap Engineering Concept for Bi³⁺ Heterovalent Doping in CsPbBr₃ Halide Perovskite

Abstract

Heterovalent CsPbBr doping with Bi results in a significant red shift of the optical absorption of both single-crystal and powdered samples. The results of low-temperature (3.6 K) photoluminescence studies of perovskite single crystals indicate that the position of the excitonic luminescence peak remains unaffected by Bi doping that, in turn, infers that the band gap of Bi-doped perovskite is not changed as well. The position and state density distribution of the valence band and Fermi level of single-crystal perovskites were determined by another direct method of ultraviolet photoelectron spectroscopy. The obtained results show that Bi doping causes no changes in the valence band structure but an increase in the Fermi level by 0.6 eV. The summary of the obtained results directly demonstrates that the concept of the band-gap engineering in Bi-doped CsPbBr halide perovskite is not valid.

Schottky/p‐n Cascade Heterojunction Constructed by Intentional n‐Type Doping Perovskite Toward Efficient Electron Layer‐Free Perovskite Solar Cells

“…Figure (d) shows the UV–Vis absorption spectra of different perovskite films, from which it is known that the band gap of the perovskite films does not change substantially with the increase in the present doping concentration range except for the local significant change in absorption intensity. This phenomenon is consistent with a recent report that heterovalent doping of CsPbBr 3 by Bi 3+ causes no band gap change but only but a shift in the Fermi level . However, the reason remains unclear presently.…”

Unlocking the Effect of Trivalent Metal Doping in All-Inorganic CsPbBr3 Perovskite

“…28 Miyasaka and co-workers have also demonstrated that the band gap of Bidoped CsPbBr3 SCs is comparable to their un-doped case; also, they found that Bi 3+ doping causes no changes in the valence band structure, but an increase in the Fermi level of 0.6 eV is observed. 29 Hence, the decrease in PL intensity suggests that Bi 3+ ions are incorporated into the CsPbBr3 host lattice and create the bulk/surface trap states. In sharp contrast, Yao and co-workers incorporated lanthanide Ce 3+ dopants into the CsPbBr3 NCs lattice and achieved a significant enhancement in PLQY of up to 89% through increasing the dopant concentration.…”

Defects and Their Passivation in Hybrid Halide Perovskites toward Solar Cell Applications

“…Bismuth has been reported to be an extremely effective means for bandgap tuning (redshift to be specific). [116] In addition, at low concentration of doping, Bi 3þ dopants have been found to fill the trap states and improve ionic conductivity of the perovskite; at a higher concentration of doping, they act as nonradiative recombination centers, leading to a transition from bimolecular recombination in pristine MAPbX 3 perovskites to a dominant trap-assisted monomolecular recombination process. [117,118] Abdi-Jalebi et al reported doping of MAPbI 3 with monovalent cations (Na þ , Cu þ , and Ag þ ) having an ionic radius similar to that of bivalent lead cations.…”