Indirect to direct band gap transition through order to disorder transformation of Cs₂AgBiBr₆via creating antisite defects for optoelectronic and photovoltaic applications

Abstract

The bandgap of Cs2AgBiBr6 is tuned to a direct bandgap by the disordering of Ag+/Bi3+ cations, creating antisite defects. The creation of antisite defects in the sublattice of double perovskites opens a new avenue for the design of photovoltaic and optoelectronic materials.

Combined DFT, SCAPS-1D, and wxAMPS frameworks for design optimization of efficient Cs2BiAgI6-based perovskite solar cells with different charge transport layers

“…1(b). The calculated lattice parameter a = 8.6338 Å is lower than that of the previously reported lattice parameter of similar double perovskitetype compound Cs 2 AgBiBr 6 (a = 11.430 Å) 59 due to the difference of atomic radius between I and Br as well as using different calculation parameters. However, the negative value of formation energy (DE f = −2.66 eV per atom) calculated by the following equation (eqn (7)) conrms the thermodynamic stability of optimized Cs 2 AgBiI 6 .…”

“…According to reports, 14,[56][57][58] several halide perovskite materials exhibit intriguing physical characteristics including structural, electrical, optical, and mechanical characteristics that make them potential candidates for optoelectronic and photovoltaic operations. Recently, Hadi et al 59 have investigated the structural, electronic, optical, and mechanical properties of lead-free cubic double perovskite-type Cs 2 AgBiBr 6 using the DFT method. The indirect band gap of Cs 2 AgBiBr 6 was reduced and switched to direct by making the compound disordered following the disordering of Ag + /Bi 3+ cations by creating an antisite defect in the sublattice.…”

“…This reduction of the band gap is responsible to enhance the optical absorption in the visible region and makes Cs 2 AgBiBr 6 suitable for solar cell applications. 59 Besides, the electronic band structure of isostructural double perovskite halide Cs 2 AgSbCl 6 has also been investigated by both the PBE and HSE approximations. 60 It was reported that Cs 2 AgSbCl 6 has an indirect band gap of 1.40 eV (HSE)/2.35 eV (PBE).…”

Emerging Chalcohalide Materials for Energy Applications

“…For example, careful nanostructuring and surface engineering could result in considerable intervalley mixing in the CBM, which positively impacted optical transitions at the band edge . Studying strain engineering and the stabilization of metastable crystalline phases might even lead to favorable optical transitions. − Additionally, it might be achieved by changing from ordered to disordered material (antisite defect), such as by disordering the cations in its sublattice. , Band offset and alignments. Only a portion of these materials have been studied for their band offset and alignments, and the majority of them remain unexplored from a device design point of view; such studies are also important to facilitate their applications in solar water splitting and solar cell.…”

“…For example, careful nanostructuring and surface engineering could result in considerable intervalley mixing in the CBM, which positively impacted optical transitions at the band edge . Studying strain engineering and the stabilization of metastable crystalline phases might even lead to favorable optical transitions. − Additionally, it might be achieved by changing from ordered to disordered material (antisite defect), such as by disordering the cations in its sublattice. , …”