Effect of Temperature on Limit Photoconversion Efficiency in Silicon Solar Cells

Abstract

The photoconversion efficiency and the temperature coefficient of an ideal silicon solar cell are investigated theoretically as a function of the base thickness. It is found that the efficiency depends nonmonotonically, whereas the temperature coefficient increases logarithmically with the thickness. Under the AM1.5 G illumination conditions at the temperature of 25 $^\circ$ C, the maximal efficiency value of 29.7% at the thickness 90 $\mu$ m is obtained. The temperature coefficient has the value of 0.234%/K at the optimal base thickness. Analogous calculations were also performed for nonideal solar cells, in which the extrinsic recombination mechanisms, doping, and parasitic series and shunt resistance play a role. It is shown that all of these factors, except for the shunt resistance, result in an increase of the temperature coefficient relative to its value obtained for an ideal solar cell. In other words, the thickness-dependent value obtained for an ideal solar cell is the theoretical lower limit of the efficiency temperature coefficient if the shunting effect is negligible. The shunting resistance, in contrast, results in a further reduction of the temperature coefficient relative to the value obtained for an ideal solar cell. The implications of these findings in the solar cell design are discussed.