Thermal Runaway in Thin Film PV: temperature profile modeling

Thermal runaway is a well known phenomena in degradation analysis of the CdS/CdTe thin film solar cells. The thin thickness of such devices can be deteriorated by the temperature fluctuations after a long enough time. We modeled the temperature profile of thin film devices considering the uniform and nonuniform distribution for temperature of the glass substrate and current flowing through TCO layer. In addition, the temperature profile of a hot spot at the edge of the device has been formulated and compared with the real data and fitting functions represented in a few literature. All the above modeling was based on the heat transfer equation considering the importance of thermal resistances. The convection and conduction resistances were introduced in the considered Biot number optimized for PV applications. The modeling presented in this paper can be extended to other solar cell structures or large scale modules. The current study suggests that the thickness and temperature dependencies of the thermal conductivity, convection and conduction resistance might be taken into account and be optimized in thermal runaway issues of thin film devices. The hot spot modeling suggests that the current flowing across the TCO layer can assist the thermal runaway and deformation of neighboring area.