Effect of disorder on transport properties in a tight-binding model for lead halide perovskites

Abstract

The hybrid organic-inorganic lead halide perovskite materials have emerged as remarkable materials for photovoltaic applications. Their strengths include good electric transport properties in spite of the disorder inherent in them. Motivated by this observation, we analyze the effects of disorder on the energy eigenstates of a tight-binding model of these materials. In particular, we analyze the spatial extension of the energy eigenstates, which is quantified by the inverse participation ratio. This parameter exhibits a tendency, and possibly a phase transition, to localization as the on-site energy disorder strength is increased. However, we argue that the disorder in the lead halide perovskites corresponds to a point in the regime of highly delocalized states. Our results also suggest that the electronic states of mixed-halide materials tend to be more localized than those of pure materials, which suggests a weaker tendency to form extended bonding states in the mixed-halide materials and is therefore not favourable for halide mixing.

Thermal fluctuations and carrier localization induced by dynamic disorder in MAPbI3 described by a first-principles based tight-binding model

“…6. The beginnings of localization behavior observed here is consistent with previous models that predict the onset of localization when disorder strengths reach a similar order of magnitude [25,26], although our predictions of the disorder strengths at 300K (potential fluctuations of 100-200 meV, Fig. 1) are numerically smaller than the values used in these previous models (500 meV in Ref.…”

“…Because of the prevalence of potential and hopping amplitude fluctuations, some amount of localization can be expected of electronic states in this system. Localization in halide perovskites has been predicted to modify finite temperature carrier properties, depending on the strength of the disorder [25,26]. We proceed to quantify the extent of localization using tight binding electronic structure obtained from the DFT-based model introduced above.…”

“…The dynamically disordered lattice [10] means atomic motion can be viewed in terms of local fluctuations [11], with fluctuations of the charged lattice and bond displacements respectively leading to fluctuations in the onsite energy and hopping of localized electronic orbitals. Several previous studies have modeled halide perovskite electronic structure with tight binding methods [19][20][21][22][23][24][25][26], using empirical modifications of equilibrium crystal structures to calculate the effects of strain [19], spin orbit coupling [19,25], spin splitting [21], or random fluctuations in onsite energies [25,26] and MA orientations [24]. However, accurate prediction of finite-temperature electronic structure requires accurate prediction of the instantaneous Hamiltonian matrix elements for a realistic thermally disordered structure.…”

How Lattice and Charge Fluctuations Control Carrier Dynamics in Halide Perovskites

“…before. 30 Strikingly, here we find that the scale of the fluctuations in the orbital overlap is sizable (on the order of 15-20% of the mean value of the hopping parameter) and generically larger than that of the on-site energy fluctuations. Fig.…”

Correlated organic–inorganic motion enhances stability and charge carrier lifetime in mixed halide perovskites

“…To deepen our understanding of the change in NA coupling arising from the thermal-induced variation of charge localization, we computed the inverse participation ratio (IPR) 70,71 of the VBM and CBM along the 1.5 ps MD trajectories for the two systems under study. The IPR of a specific KS state is defined as , which characterizes the degree of charge localization of a given KS orbital.…”