Experimental investigation on the characteristics of a solar cell under different illumination intensities and shading areas

Abstract

The characteristics of a solar cell, the short-circuit current (I _sc ), the open-circuit voltage (V _oc ), the maximum power point (V _m , I _m ), the fill factor (FF) and the photoelectric conversion efficiency (η) under different illumination intensities and shading areas have been experimentally investigated. The work factor ω is given by ω = (1 - A/A ₀) × S/S ₀, where A ₀ is the total solar cell area, A the shading area, S ₀ the benchmark reference irradiation level, and S the new level of the irradiation, is introduced to take the light intensity and shading area into account. The results show that Isc and Im increase on an approximately linear increasing way with ω, but V _oc and V _m approach the saturation levels. The reason is that the current is a linear function of ω, and the relationship of the voltage to ω is logarithmic. We also found I _sc (V _m ) to depend more on ω than I _m (V _oc ). In addition, we observed that η tended to increase linearly with ω, but FF tended to converge to saturation. The reason for the behavior of η is the reduction in the contact resistance and in the electron-hole recombination with increasing ω. However, FF is mainly determined by V _oc . The improvement in the solar cell performance with increasing ω results from an increase in the current, but not in the voltage or the fill factor.