Optimization of light spot intensity and coverage to a triple-junction solar cell under non-uniform illumination

Abstract

The cells in high concentrated photovoltaic module are usually high efficiency triple-junction solar cells. Due to the non-ideal concentrators, the light intensity distribution on a solar cell is highly non-uniform, so the appropriate increase of the ratio between light spot size and cell area is a method to reduce the influence of non-uniform illumination on the electrical performance of the solar cell. The circuit network model is used to calculate the influences of light spot intensity distribution and size on a triple-junction solar cell. The light spot intensities and sizes, the cell efficiencies, and the temperature distributions of the cell under four design schemes (uniform illumination, non-uniform illumination, maximum cell efficiency, and maximum module efficiency) are compared. The results show that the cell efficiency in the maximum module efficiency design is not the maximum cell efficiency under the standard testing condition. The design to make the cell achieve the maximum efficiency obtains the minimum module efficiency. The design to achieve maximum module efficiency has a smaller size of concentrator, so the cost of the module goes up. The design to achieve the maximum cell efficiency has a bigger size of concentrator and a lowest cell temperature, so the cost of the module will reduce and the reliability will improve. Above all, the requirement of electricity quantity should be fully considered in the module design, in which an appropriate geometric concentration ratio and light spot coverage to solar cells should be chosen.