Study of recombination mechanisms in organic solar cells by electroluminescence and light ideality factor

Abstract

The performance of solution-processed organic solar cells is often limited by various recombination pathways. In this scenario ideality factor (nid) act as a signature for identification of different loss mechanisms in these solar cells. A detailed analysis of open circuit voltage (Voc) dependence on illumination intensity as well as electroluminescence (EL) dependence on the injected currents can provide the value of ideality factor. We have carried out this study for identification and quantification of dominant recombination loss mechanism in crystalline Si and organic solar cells. The obtained ideality factor by these two methods support each other which validates the result. On the basis of these studies, it has been concluded that the major energetic loss in bulk heterojunction (BHJ) based organic solar cell arises due to its low radiative efficiency (QLED) and non-radiative recombination loss mechanism at donor/acceptor interface and semiconductor/electrode interfaces. So the performance of the organic solar cells can be improved by optimizing the semiconductor-electrode energy alignment, and surface morphology near contacts