A theoretical study of influence of charge carrier mobility in PTB7:PC71BM bulk heterojunction organic solar cells

Abstract

In this study, an optoelectronic model is presented to simulate the structure of PTB7:PC71BM organic solar cells. This model is based on transfer matrix model for calculating optical processes and drift–diffusion model for computing both electrical and charge transport processes; the latter includes the effects of energetic disorder. In the presence of energetic disorder, the total recombination is calculated as the sum of Langevin recombination, recombination via charge transfer states, and recombination via exponential tail states. We investigate the influence of charge carrier mobility on photovoltaic parameters, charge transport, and recombination rate. Simulation results indicate that open circuit voltage is governed by the charge carrier mobility and power conversion efficiency as a function of charge carrier mobility has a maximum value at μ = 10−2 (cm2/Vs). Simulated current density–voltage curve reveals good agreement with published experimental results. The open circuit voltage is calculated as a function of generation rate. It is found that the slope of lines increases with decreasing the charge carrier mobility.