IMPROVEMENTS IN SUNLIGHT TO ELECTRICITY CONVERSION EFFICIENCY: ABOVE 40 FOR DIRECT SUNLIGHT AND OVER 30 FOR GLOBAL

摘要

The key to reducing photovoltaic costs is continual improvement in energy conversion efficiency. The most successful approach to increasing this efficiency is to split sunlight into spectral bands and use a dedicated solar cell to convert each band efficiently. Recently, we demonstrated sunlight to electricity conversion with confirmed efficiency above the 40% landmark for the first time, using a 287-cm~2 aperture area sub-module, notably by innovative use of commercial Ⅲ-Ⅴ and silicon concentrator solar cells. This device was a prototype for a large photovoltaic power tower, where sunlight is reflected from a field of sun-tracking heliostats to a dense photovoltaic array mounted on a central tower. In this paper, we describe the outcomes from work directed at demonstrating further sunlight conversion efficiency improvements, both by extending the above approach and by applying similarly innovative ideas to one-sun modules, with ＞30% minimodule efficiency recently demonstrated.