A detailed analysis on the heat generated inside c-Si solar cell

Abstract

The heat generated inside solar cells is one of the important factors influencing the operational stability of a photovoltaic system composed of solar cells. In this work, based on the influencing factors of four main heat-generated mechanisms inside c-Si solar cells, i.e., the energy relaxation process of the hot carrier, Joule heat, recombination heat, and Peltier and Thomson effects, the distribution features of the heat generated by each mechanism are first discussed, and then, considering two common working conditions of c-Si solar cells in module form, i.e., the variations of environmental temperature and output voltage, the changing rules of the distributions of heat generated by different mechanisms are analyzed. The general features of the heat distributions of c-Si solar cells are that the obviously absorbed and released heat only exists in the regions near the front and back surfaces; the four mechanisms all release heat in the narrow n region close to the front surface; and Peltier and Thomson effects are the only mechanism of absorbed heat in the wide p region. The offset effects between released and absorbed heat make the total heat generated by the four mechanisms very small in the wide p region. With the environmental temperature increasing, the heat distribution features of each heat mechanism will remain unchanged, and except for the heat generated by the energy relaxation of the hot carrier, the released and absorbed heat generated by other mechanisms will increase in the whole c-Si active layer. With the output voltage increasing from 0 to 0.68 V, aside from the heat distribution of the energy relaxation of the hot carrier, the distributions of heat generated by other mechanisms show obvious threshold voltage effects, and only when the output voltage is larger than the threshold voltage will the heat distributions of different mechanisms be significantly changed by the variations of the output voltage.