A Loss Analysis for a 28% Efficient 520X Concentrator Module
A module efficiency loss analysis has been conducted by comparing the efficiency of the module on-sun (28.2% peak) to the efficiency of the bare cell measured in the laboratory (35.5% peak). This analysis suggests that there are two main loss mechanisms in the module: elevated operating temperature and an optical efficiency less than unity. This analysis also suggests that the effects of spectral and intensity non-uniformity have been well controlled
III-V Solar Cells and Concentrator Arrays
Semiconductor heterostructures allow solving the problems of controlling the fundamental parameters of semiconductor devices owing to the possibility of change in the electronic band structure, bandgaps and refractive indices of a material itself during epitaxial growth, as well as effective masses and mobilities of charge carriers in it.
Effects of concentrator chromatic aberration on multi-junction cells
Most practical photovoltaic concentrator optics have considerable chromatic aberration. Thus in a two-junction monolithic cell, the pattern of current generation in the high-bandgap junction is different from that in the low-bandgap junction, resulting in an attempted current flow parallel to the junction in the tunnel junction and adjacent layers. Sheet resistivity of these layers is too high to support this lateral current flow, so at each point on the cell, the current is limited to the current generated in the lowest-current junction. This results in a substantial loss in cell output unless the chromatic aberration of the optics is somehow compensated for. Using a software model, the authors have examined the losses caused by chromatic aberration, and have designed two types of concentrator optics which meet the spectral uniformity needs of multijunction solar cells. One is for space applications where weight is an overriding concern. The other is for terrestrial use where cost and a low sensitivity to construction and operating tolerances are paramount.