Temperature Dependence of Bandgap in Lead‐Halide Perovskites with Corner‐Sharing Octahedra

Understanding the molecular origin of the atypical temperature dependence of bandgap (i.e., bandgap renormalization) in lead‐halide perovskites with corner‐sharing octahedra is of fundamental interest and a prerequisite for their applications in fabricating high‐performance optoelectronic devices. The bandgap renormalization is attributed to the lattice thermal expansion and electron–phonon interactions. However, it remains controversial whether the thermal expansion has a negligible effect on the band‐edge structure of corner‐sharing [PbX6]4− (X = halide anion) octahedra in perovskites, relative to the electron–phonon interactions. In this review, this issue is clarified by focusing upon the most recent theoretical advances in the field of investigating the bandgap renormalization in perovskites. The timely research progress on the modulation of bandgap renormalization through the structural engineering in perovskites is also outlined. Finally, a vision about the directions for further in‐depth research in this field is provided, with the intent of promoting a more profound understanding and controlling of bandgap renormalization in perovskites in the future. The origin of temperature dependence of bandgap in lead‐halide perovskites can be ascribed to the thermal expansion and electron–phonon interactions (including the Debye–Waller and self‐energy terms) in the corner‐sharing [PbX6]4− (X = halide anion) octahedra. Herein, the most recent theoretical and experimental advances in the field of exploring the bandgap renormalization behavior in perovskites are reviewed.