Design Principles for the Atomic and Electronic Structure of Halide Perovskite Photovoltaic Materials: Insights from Computation

Abstract

In the current decade, perovskite solar cell research has emerged as a remarkably active, promising, and rapidly developing field. Alongside breakthroughs in synthesis and device engineering, halide perovskite photovoltaic materials have been the subject of predictive and explanatory computational work. In this Minireview, we focus on a subset of this computation: density functional theory (DFT)-based work highlighting the ways in which the electronic structure and band gap of this class of materials can be tuned via changes in atomic structure. We distill this body of computational literature into a set of underlying design principles for the band gap engineering of these materials, and rationalize these principles from the viewpoint of band-edge orbital character. We hope that this perspective provides guidance and insight toward the rational design and continued improvement of perovskite photovoltaics.

Absolute energy level positions in tin- and lead-based halide perovskites

“…Our tight-binding analysis focuses on the VBM and the CBM. The analysis becomes more straightforward if one concentrates on cubic symmetry and uses the symmetry analysis presented by Boyer-Richard et al 19 . For cubic perovskites (space group P m-3m ) the VBM and CBM are situated at the R-point of the Brillouin zone, and one can restrict a tight-binding analysis to states at the R-point.…”

“…3c, and two hybridization strengths, between the M, s and X, p orbitals, and between the M, p and X, s orbitals, respectively. Interactions between M, s and X, s orbitals, and between M, p and X, p are symmetry forbidden at the R-point of a cubic perovskite, so we do not have to consider the corresponding hybridization strengths 19 . The energy levels of the halide ions, E X, s , E X, p , can be obtained from the DFT-calculated level spectra at the Γ-point or the R-point, by identifying halide states that are non-bonding in cubic perovskites.…”

Highly Efficient Blue‐Emitting CsPbBr3 Perovskite Nanocrystals through Neodymium Doping

“…[14,18,22] However, detailed experimental studies also provide clear evidence that lattice contraction leads to a redshift while octahedral tilting leads to blueshift. [42][43][44] To understand the redshift induced by structural changes, we note that when Pb is exchanged with Nd, lattice contraction is caused by the charge redistribution from the Nd toward the neighboring Pb-Br pairs as Nd has smaller electronegativity than Pb. With decreasing Pb-Br bond length, the antibonding interaction between the Pb 6s and Br 5p states building the VBM increases, which in turn shifts the band toward higher energies.…”

Effect of Anisotropic Confinement on Electronic Structure and Dynamics of Band Edge Excitons in Inorganic Perovskite Nanowires

“…In order to better understand the band-edge structure, polarization-resolved PL measurements of single bundles could be performed at low temperature, which would produce sharper emission peaks 52 and remove the confounding effect of nanowire bundle orientation. 53 Such measurements should be supplemented with electronic structure calculations 54 of CsPbBr 3 nanowires with various crystal structures and growth directions, similar to calculations that have been done for near-cubic nanostructures. 55…”