Theoretical analysis of electron transport in perovskite thin films

Abstract

Inherent disorder in perovskite films has been suggested as a factor that improves exciton separation. At the same time, the disorder can potentially disrupt electron flow, deteriorating device performance. In this paper, we study the role of disorder in electron transport in perovskite films using kinetic Monte Carlo simulations. The effect of temperature on the conductivity of the system is studied. We find that at room temperature, where most solar cells operate, the effect of disorder on the conductivity is minimal. At lower temperatures, current flows along specific paths in the film. In contrast, the ability of carriers to sample all sites in the film at room temperature allows realisation of higher device efficiencies. We find that conductivity obeys Mott's expression for variable range hopping σ(T) ∝ T⁻¹e^{−(T_o/T)1/3}. The value of the universal proportionality constant α₂ associated with the characteristic temperature has been computed. The effect of electric field on transport has also been studied. The average hopping distance is found to increase with the increase in the electric field at low temperatures, although this dependence is not observed at room temperature. Likewise, the conductivity is also a function of applied field F, and is found to be obey σ(F) ∝ F^−1/3e^{−(F_o/F)1/3} at low temperatures while being field-independent at room temperature.