Determining the bandgap and energetic disorder of photoactive layer via modeling the photovoltaic performance of organic solar cells

Abstract

The bandgap and energetic disorder of photoactive layer are of great importance to analyzing the energy losses of organic solar cells (OSCs). However, the accurate determinations of these two parameters have yet to be realized so far. Here, an improved analytic model based on Shockley equation is provided to simulate the photovoltaic performance of nonfullerene OSCs with efficiencies of ∼19%, whereby the bandgap and energetic disorder as fitting parameters are deduced. The modeling indicates that the radiative voltage loss is major, relative to the nonradiative one. The accurate quantification of the bandgap and energetic disorder relies on the accurate experimental measurement of charge carrier mobilities of photoactive layer. The simulations show that the state-of-art nonfullerene photoactive layers have bandgaps of ∼1.35 to 1.37 eV and energetic disorders of ∼0.11 eV. In order to improve the efficiencies of OSCs to over 20%, it is proposed to decrease the energetic disorders and/or increase the charge-carrier mobilities of photoactive layers.