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

Abstract

Metal halide perovskites are promising materials for future optoelectronic applications. One intriguing property, important for many applications, is the tunability of the band gap via compositional engineering. While experimental reports on changes in absorption or photoluminescence show rather good agreement for different compounds, the physical origins of these changes, namely the variations in valence and conduction band positions, are not well characterized. Here, we determine ionization energy and electron affinity values of all primary tin- and lead-based perovskites using photoelectron spectroscopy data, supported by first-principles calculations and a tight-binding analysis. We demonstrate energy level variations are primarily determined by the relative positions of the atomic energy levels of metal cations and halide anions and secondarily influenced by the cation-anion interaction strength. These results mark a significant step towards understanding the electronic structure of this material class and provides the basis for rational design rules regarding the energetics in perovskite optoelectronics.

Effect of chemical nature of atoms on the electronic, dielectric, and dynamical properties of ABX3 halide perovskite

“…Meanwhile, Z * of A cation practically remains the same, close to its nominal charge +1. Same results are found in the work of Tao et al, whereby using Crystal Orbital Hamiltonian Population (COHP) analysis, they concluded that the covalent bonding is dominated by Pb and I contributions and no contribution of Cs.…”

“…The increase of CBM energy may be due to the decrease of the interatomic interaction between p − B and p − X in the conduction band, where the energy of p − B increases from I to Br to Cl , and this is due to that going from I to Br to Cl , the B − X distances decrease, hence an electron on a B atom is more confined and its energy increases . However, from Table S2 and results found in recent work of Tao el al., 56 in a case of replacing Pb by Sn , the shift of VBM is more than of CBM, and this is due to that the shifting of s state is larger than that of the p state . The lagre shift of VBM and CBM when we change B atoms comparing by changing X atoms may explain the large decrease of the bandgap produced by the change of the B cation.…”

Theoretical and experimental investigations on the bulk photovoltaic effect in lead-free perovskites MASnI3 and FASnI3

“…14 For the FASnI 3 perovskite, we adopted a tetragonal phase structure with lattice parameters of a ¼ 8.79 A, b ¼ 8.99 A, and c ¼ 12.83 A. 15 Firstly, we optimized the crystal geometry structure by the energy lowest theory, aer then, we calculated and analyzed the energy band and density of state base on the optimized results, although the lattice parameters don't derive their lattice vectors in a self-consistent manner, 32 we think the way is reasonable. We also calculated the optical properties and dielectric function of the two perovskite materials.…”

“…Under high humidity or strong light exposure, the structural phase was stable through utilizing additive, and SnF 2 played a signicant role in the device, but addition of excess SnF 2 has also a tendency to form a separate phase on the surface of perovskite lms. In addition, some literatures 14,15 have analyzed the reason why the FASnI 3 's PCE was higher than the MASnI 3 's efficiency, however, these viewpoints are more and different.…”

Engineering 3D perovskites for photon interconversion applications

“…Lead-based perovskites have the 'correct' band alignment for exothermic hole transfer, as well as slightly exothermic electron transfer. The desired low bandgap tin-based perovskites have shallower valence and conduction bands [83], which disallow free carrier sensitization, and would only enable triplet sensitization by bound excitons. However, excitons rapidly dissociate in these materials, therefore this pathway is not expected to be efficient.…”