The nature of the lead-iodine bond in PbI2: A case study for the modelling of lead halide perovskites

Abstract

A detailed knowledge of the basic electronic interactions in lead halide perovskites components (PbI2 and methylammonium iodide) can possibly drive enhanced solar cell efficiency. We report an extensive investigation on the electronic structure and nature of the chemical bond in the PbI2 perovskite precursor, both in gas and solid state, together with a comparison with available experimental data, which allows to effectively calibrate the computational framework, along with gaining basic understanding on the nature of the Pb I chemical bond. Inclusion of spin orbit coupling and calibrated HF exchange contribution to the DFT hybrid functional are proved essential for an accurate description of the electronic structure of both molecular and solid state PbI2. Such computational framework, calibrated on the model PbI2 system, can be directly translated to the accurate description of the electronic band structure of the prototypical methylammonium lead-iodide perovskite, setting the basis for the trustful modelling of different lead-halide perovskites. Graphical abstract

Formation of lead halide perovskite precursors in solution: Insight from electronic-structure theory

“…For comparison, PbX 2 in an implicit solvent cavity without solvent molecules attached is also considered. The results obtained for the latter systems confirm the net charge transfer between lead and halogen atoms and hence ionic nature of the Pb-X bond [65]. The trend shown in Fig- ure 4b) indicates an increasingly negative charge in the less electronegative halogen atoms, with variations on the order of 0.1e − .…”

Formation of Lead Halide Perovskite Precursors in Solution: Insight from Electronic‐Structure Theory

“…The results obtained for the latter systems confirm the net charge transfer between lead and halogen atoms and hence the ionic nature of the Pb─X bond. [71] The trend shown in Figure 4b indicates an increasingly negative charge in the less-electronegative halogen atoms, with variations on the order of 0.1 e À . This finding is in agreement with earlier experimental observations.…”

First-principles analysis of the optical properties of lead halide perovskite solution precursors

“…[27], a lower absorption onset of PbI 2 (GBL) 4 compared to PbI 2 (DMSO) 4 is reported for measurements of these compounds in the presence of the methylammonium cation. The systematic blue-shift of our computed spectra with respect to experimental references is to be mainly ascribed to the absence in our calculations of the non-negligible contributions of spin-orbit coupling [65] and to the absence of additional intermolecular interactions beyond those between the PbX 2 backbones and the nearest-neighboring solvent molecules. However, as demonstrated in Ref.…”