Role of Chemistry and Crystal Structure on the Electronic Defect States in Cs-Based Halide Perovskites

Abstract

The electronic structure of a series perovskites ABX3 (A = Cs; B = Ca, Sr, and Ba; X = F, Cl, Br, and I) in the presence and absence of antisite defect XB were systematically investigated based on density-functional-theory calculations. Both cubic and orthorhombic perovskites were considered. It was observed that for certain perovskite compositions and crystal structure, presence of antisite point defect leads to the formation of electronic defect state(s) within the band gap. We showed that both the type of electronic defect states and their individual energy level location within the bandgap can be predicted based on easily available intrinsic properties of the constituent elements, such as the bond-dissociation energy of the B–X and X–X bond, the X–X covalent bond length, and the atomic size of halide (X) as well as structural characteristic such as B–X–B bond angle. Overall, this work provides a science-based generic principle to design the electronic states within the band structure in Cs-based perovskites in presence of point defects such as antisite defect.

Evaluating Pb-based and Pb-free Halide Perovskites for Solar-Cell Applications: A Simulation Study

“…However, due to the less electronegativity difference between Pb & I, bond length increases with a lower band gap in CsPbI 3 than in Sn-halide perovskites. It complies with the above statement that the change in the bond length of B & X leads to the tuning of the band-gap [ 37 ]. Therefore, it is observed that Cs-based all-inorganic (CsPbI 3 & CsSnI 3 ) perovskite quantum dots show better performance, high PL quantum yield, narrow emission bandwidth, significant extinction coefficient, crystal defect tolerance, and good stability against moisture and oxygen as compared to organic-inorganic hybrid perovskite quantum dots [ 38 ].…”

Investigation of Hybrid Electrodes of Polyaniline and Reduced Graphene Oxide with Bio-Waste-Derived Activated Carbon for Supercapacitor Applications

“…This can be explained by the formation of PAni into the OS−rGO surface, as the pore volumes for both the PAni@OS−rGO (1:1) (0.59 cm 3 •g −1 ) and PAni@OS−rGO (2:1) (0.51 cm 3 •g −1 ) are relatively high, whereas the OS−rGO and PAni have pore volumes of 0.62 cm 3 •g −1 and 0.16 cm 3 •g −1 , respectively. Generally, the S BET of the composites increases with their porosity [36,37].…”

Charge Compensation by Iodine Covalent Bonding in Lead Iodide Perovskite Materials

“…An understanding of perovskite defects begins with individual lattice site defects including halide vacancies (V X ) [15][16][17], A-site vacancies (V A ) [18], and halide interstitials (X i ) [15,19]. Larger defects have been proposed as well, including Schottky (V X + V A ) [20], Frenkel (V X + X i ) [21,22], and iodine trimer (I 3 ) [14,19,[23][24][25][26] defects.…”

“…Structural representations of perovskite lattices have developed from pure-cubic (monomorphic) [37] to stochastic approximations for free rotation of A-site cations and octahedral tilting (polymorphic) [38]. From electronic structure calculations, atomic charges can be calculated through Bader charge analysis [26,39]. Bader charge analysis is a fully ab initio method for the calculation of atomic charges and assignment of oxidation states based upon a topological analysis of the electron charge density of the system [40,41].…”