Temperature dependence of the open-circuit voltage of an N +-P-P + silicon solar cell under high illumination levels

Abstract

The effect of the temperature-dependent solar cell parameters on the open-circuit voltage of n +-p-p + solar cells at medium and high levels of illumination is studied. The effects of temperature variations in the intrinsic carrier concentration, mobility, absorption coefficient, excess carrier lifetime and energy band gap shrinkage are incorporated to analyse the variation in the open-circuit voltage with temperature. To calculate the n +-p and p-p + junction voltages, the condition of equal current densities at the two junctions is numerically solved for the voltages under open-circuit conditions. Using these two voltages and the Dember potential, which appears in the p-type base region of the cell, the total open-circuit voltage is calculated for the temperature range 0 – 100°C. The n +-p junction voltage decreases while the p-p + junction and Dember voltages increase slowly with increasing temperature. The effect of all the voltages is such that the total open-circuit voltage decreases with increasing cell temperature. The decrease in the open-circuit voltage with increasing temperature at low and medium levels of illumination is larger than that at high levels of illumination. This effect is explained in terms of the different behaviours of the open-circuit voltages for n +-p and p-p + junctions.