Intensity dependency of photovoltaic cell parameters under high illumination conditions: An analysis

Abstract

Previously, an analytical method was developed to extract the photovoltaic (PV) cell parameters, such as the shunt resistance, Rsh, series resistance, Rs, diode ideality factor, n, and reverse saturation current density, J0, through the use of the single current density-voltage (J-V) characteristics under high illumination conditions. Accurate knowledge of the PV cell parameters under different illumination conditions is of vital importance to PV design and performance. Although several attempts have been made to examine the dependency of the PV cell parameters on the illumination intensity Pin, there are no reports on the dependence of the PV cell parameters on Pin under high illumination conditions. In this regards, dependency of the analytically-predicted PV cell parameters on Pin of Si solar cells with various structures has been investigated. The analytically-predicted values of Rsh and Rs decreased with increasing Pin. The rate of change in Rsh, however, was higher than that of Rs. The decrease in Rsh may be due to light induced degradation of PV cells. The decrease in Rs values might be due to an increase in the conductivity of the active region. On the other hand, n and J0 increased with increasing Pin. This increase in n and J0 might have a savior effect, reducing the curve factor CF and hence the performance of the PV cell. The rate change in all PV cell parameters was higher at lower Pin values than at the higher Pin values. The theoretically computed values of the open circuit voltage Voc, curve factor CF and efficiency η using this method showed good agreement with the experimentally measured values at various Pin. The performance of the PV systems is dependent on the product of the Jsc, Voc and CF. Therefore, it is important to determine the optimal value of Pin to achieve the maximum output power (minimum losses due to Rsh, Rs, n and J0) from a PV system. By doing so, the cost per peak watt of solar energy can be minimized by enhancing the performance of PV systems. © 2014 Elsevier Ltd.