Abstract
The photo-degradation mechanism of P3HT:PCBM bulk heterojunction solar cells is investigated by using the AMPS-1D (analysis of microelectronic and photonic structures) computer program. An effective medium model with exponential tail states and Gaussian mid-gap states is used to simulate the J-V characteristics of the photovoltaic devices. By using the proposed model, the J-V characteristics of both fresh and degraded devices could be nicely reproduced. The simulation results suggest that the main factors governing the mechanism of photo-degradation are the increase in the density of the mid-gap states, the increase of the p-type doping concentration, the slight increase in back contact barrier height and the reduction of charge carriers mobility. The deterioration of the photovoltaic performance is attributed to the increased recombination rate and insufficient charge collection. (C) 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim