Bimetallic superalkali substitution in the CsPbBr3 perovskite: Pseudocubic phases and tunable bandgap

Abstract

Perovskites attract attention as efficient light absorbers for solar cells due to their high-power conversion efficiency (up to 24%). The high photoelectric conversion efficiency is greatly affected by a suitable band structure. Cation substitution can be an effective approach to tune the electronic band structure of lead halide perovskites. In this work, superalkali cations were introduced to replace the Cs+ cation in the CsPbBr3 material. The bimetallic superalkalis (LiMg, NaMg, LiCa, and NaCa) were inserted since they are structurally simple systems and have a strong tendency to lose one electron to achieve a closed-shell cation. The cation substitution in the lead halide perovskite leads to changes in the shape of both valence and conduction bands compared to CsPbBr3. Introducing superalkali cations produces extra electronic states close to the Fermi level, which arise from the formation of alkali earth metal states at the top of the valence band. Our first-principles computations reveal that bimetallic superalkali substitution decreases the bandgap of the perovskite. The bandgaps of MgLi–PbBr3 (1.35 eV) and MgNa–PbBr3 (1.06 eV) are lower than the bandgap of CsPbBr3 (2.48 eV) and within the optimal bandgap (i.e., 1.1–1.4 eV) for single-junction solar cells. Thus, the MgLi–PbBr3 and MgNa–PbBr3 inorganic perovskites are promising candidates for high-efficiency solar cells.

Composition Engineering in CsPb1–xGexBr3 Perovskite Light-Emitting Diodes for Stable and Efficient Performance

“…Additionally, the P 4/ mbm space group represents a stable state with lower energy, which is commonly studied in experimental investigations. Similarly, Figure c illustrates that the R 3 m space group (rhombohedral structure) serves as the most stable state for the CsGeBr 3 system, in agreement with previous literature reports. , Figure b presents an energy diagram showcasing different space groups of CsPb 0.5 Ge 0.5 Br 3 . This diagram is constructed using a supercell doped with 50% Ge ions.…”

Tuning the electronic structure of gold cluster-assembled materials by altering organophosphine ligands

“…Our results confirm that the accuracy of HL gap calculations can be enhanced by using hybrid functionals. 37 In particular, the HL gap estimated for Au 32 ( n Bu 3 P ) 12 Cl 8 is 1.35, 0.74, and 0.42 eV for PBE0-D3, HSE06-D3, and PBEsol, respectively. Since the experimentally obtained bandgap for Au 32 ( n Bu 3 P ) 12 Cl 8 solid is 1.55 eV, 10 the PBEsol approach leads to a significantly underestimated (by 73%) bandgap value, whereas HSE06-D3 underestimates the HL gap by 52%.…”

“…Our results confirm that the accuracy of HL gap calculations can be enhanced by using hybrid functionals. 37 In particular, the HL gap estimated for Au 32 ( n Bu 3 P) 12 Cl 8 is 1.35, 0.74, and 0.42 eV for PBE0-D3, HSE06-D3, and PBEsol, respectively. Since the experimentally obtained bandgap for Fig.…”

Design and Investigation of Superatoms for Redox Applications: First-Principles Studies

“…Cation (A) substitution can be an efficient approach to adjust the electronic band structure of lead halide CsPbBr 3 perovskites. The examples include introducing superalkali cations to replace the Cs + cation in the CsPbBr 3 material [ 61 ]. The bimetallic superalkalis (LiMg, NaMg, LiCa, and NaCa) were chosen since they are structurally simple compounds and have a strong tendency to detach one electron (IE = 4.57–4.92 eV [ 62 ]) to achieve a closed-shell cation.…”