Exact Analytical Solution for Organic Solar Cells Showing S-Shaped J-V Characteristics Using Special Trans Function Theory (STFT)

Abstract

Many organic solar cells exhibit anomalous kinks showing S-shaped J-V behaviour. This atypical behaviour may be electrically modelled by including a second diode (D2) with opposite current characteristics together with a shunt resistance to that of the conventional solar cell diode (D1). In this communication, we present an exact analytical expression for the cell’s output voltage as an explicit function of its terminal current by the application of special trans function theory (STFT) for the S-shaped J-V characteristics model. The explicit nature of the proposed solution avoids approximations and numerical iterations. The differentiability of the trans function in STFT facilitates the analytical analysis of the problem. The evolution of the S-shaped J-V characteristics and the fill factor (FF) is also deliberated by varying different parameters to validate the proposed analytical solution.