Related Experiment Video
Updated: Sep 23, 2025
Solution-Processed "Silver-Bismuth-Iodine" Ternary Thin Films for Lead-Free Photovoltaic Absorbers
Published on: September 27, 2018
Thermochromic Cs2 AgBiBr6 Single Crystal with Decreased Band Gap through Order-Disorder Transition
Yaru Zhang1,2, Yilong Song3, Yuan Lu4
1State Key Laboratory of High Performance Ceramics and Superfine Microstructure, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai, 200050, China.
Abstract:
Lead-free Cs2 AgBiBr6 double perovskite is considered to be a promising alternative to the traditional lead-based analogues due to its long carrier lifetime, high structural stability, and non-toxicity. However, the large band gap limits its absorption of visible light, which is not conducive to further optoelectronic applications. Herein, a thermochromic strategy is reported to decrease the band gap of Cs2 AgBiBr6 by approximately 0.36 eV, obtaining the smallest reported band gap of 1.69 eV under ambient conditions. The experimental data indicate that after annealing the Cs2 AgBiBr6 single crystals at 400 °C, the silver (Ag) and bismuth (Bi) atoms occupy the B-site in a random way and form a partially disordered configuration. The formation of the antisite defects broadens the band edges and decreases the band gap. This work offers new insights into the preparation of narrow band gap lead-free double perovskites, and a deep understanding of their structural and electronic properties for further development in photoelectric devices.
More Related Videos
Related Concept Videos
02:58Crystal Field Theory - Octahedral Complexes
To explain the observed behavior of transition metal complexes (such as colors), a model involving electrostatic interactions between the electrons from the ligands and the electrons in the unhybridized d orbitals of the central metal atom has been developed. This electrostatic model is crystal field theory (CFT). It helps to understand, interpret, and predict the colors, magnetic behavior, and some structures of coordination compounds of transition metals.
CFT focuses on...
01:16Thermal Sigmatropic Reactions: Overview
Sigmatropic shifts are classified based on an order term [i, j ], where i and j indicate the number of atoms across which each end of the σ bond migrates. Below are examples of a [3,3] sigmatropic shift in...
01:22Semiconductors
Metals such as copper (Cu), zinc (Zn), or lead (Pb) have low resistivity and feature conduction bands that are either not fully occupied or overlap with the valence band, making a bandgap non-existent. This allows electrons in the highest energy levels of the valence band to easily transition to the conduction band upon gaining...
01:01Energy Bands in Solids
Band Formation:
When atoms are brought close together, as in a solid, these discrete energy levels begin to split due to the overlap of electron orbitals from adjacent atoms. This split occurs because of the Pauli exclusion principle, which states...
02:46Crystal Field Theory - Tetrahedral and Square Planar Complexes
Crystal field theory (CFT) is applicable to molecules in geometries other than octahedral. In octahedral complexes, the lobes of the dx2−y2 and dz2 orbitals point directly at the ligands. For tetrahedral complexes, the d orbitals remain in place, but with only four ligands located between the axes. None of the orbitals points directly at the tetrahedral ligands. However, the dx2−y2 and dz2 orbitals (along the Cartesian axes) overlap with the ligands less than the dxy,...
02:35Band Theory
The energy difference between these bands is known as the band gap.
Conductor, Semiconductor,...