Origin of Low Carrier Mobilities in Halide Perovskites

Abstract

Halide perovskites constitute a new class of semiconductors that hold promise for low-cost solar cells and optoelectronics. One key property of these materials is the electron mobility, which determines the average electron speed due to a driving electric eld. Here we elucidate the atomic-scale mechanisms and theoretical limits of carrier mobilities in halide perovskites by performing a comparative analysis of the archetypal compound CH 3 NH 3 PbI 3 , its inorganic counterpart CsPbI 3 , and a classic semiconductor for LEDs, wurtzite GaN, using cutting-edge many-body ab initio calculations. We demonstrate that low-energy longitudinal-optical phonons associated with uctuations of the Pb-I bonds ultimately limit the mobility to 80 cm 2 /Vs at room temperature. By extending our analysis to a broad class of compounds, we identify a universal scaling law for the carrier mobility in halide perovskites, and we establish the design principles to realize high-mobility materials.

Direct evidence of weakly dispersed and strongly anharmonic optical phonons in hybrid perovskites

“…This phonon scattering is believed to be the key fundamental factor in establishing the intrinsic limit of the charge carriers mobility. More specifically, it has been recently suggested that this limit is set by the lower energy LO modes (3-20 meV) [58]. Therefore, the observed presence of such modes, common in all four compounds, seems to be the reason for the relatively low mobilities compared to classical inorganic semiconductors like Si and GaAs.…”

“…By crossreferencing our results with the above mentioned previous works and other literature on the subject, we can assign the identified features of the low temperature spectra to the respective vibrational modes. In recent lattice dynamics calculations, Ponce et al [58] predict five modes for MAPI at 3, 4.3, 10.2, 14.4 and 21 meV. Asite displacement (i.e.…”

All‐Inorganic CsPbX3 Perovskite Solar Cells: Progress and Prospects

“…[41,42] Small and comparable effective masses of the electrons and holes can be predicted from the electronic band dispersion around the band edges,w hich contribute to the carrier mobilities. [43] However these mobilities,i nt he Pb-based HaPs in general, are considerably smaller than expected from the values of effective mass,a nd it has been suggested that this is due to phonon scattering by the relatively soft HaP lattice. [44] As the crystal cubic phase is transformed to the low-symmetry orthorhombic phase,t he metal-halide-metal bond angle decreases.A long with the increase in the E g ,t his decrease in bond angle increases both the effective carrier masses and Reproducedw ith permission.…”

Hole mobility of strained GaN from first principles

“…As discussed in Ref. 66, the accuracy of the effective masses is improved by using a self-consistent, kdependent scissor shift. This approximation, which we call G 0 W 0 -∆ k , yields a wider bandgap of 3.85 eV.…”