Temperature of solar cells in reverse bias: Theory and applications

Solar cells are reversely biased, consume power generated by neighbor cells and become hot when they are shaded or do not function properly. It is necessary to quickly measure their temperatures and accurately estimate them for screening. This paper presents the theory behind thermal emission measurement under constant current reverse bias and estimation methods of steady state temperatures of cells and modules. A simple physical model describes thermal emission measurement system based on knowledge that heat is transferred by heat convection, conduction and radiation and the power is fed by electrical bias. We confirm the model by short time thermal emission measurement and electrical current voltage characterizations. A quantitative and quick estimation method of steady state temperatures is presented based on the model. This model applies to estimate the temperature of modules by incorporating thermal resistance. The results also suggest that low temperature can be achieved by low reverse voltage or low thermal resistance. This study helps to understand physics behind reversely biased solar cells to develop a quick and convenient method to estimate steady state temperature of cells and modules.