oa Recent progress in wide bandgap materials GaN/InGaN for concentrated photovoltaics

In recent years, concentration has been adopted as a promising strategy to high $/W ratio of photovoltaic energy conversion. In concentrated photovoltaics, the Sun's energy is focused into a smaller area allowing for the conversion of sunlight into electricity using only a small low-cost photovoltaic cell. Conventional solar concentrators, which use III-V are, however, costly to produce. Ideally, the material should perform well under high concentration and be affordable. We propose to construct solar cells based on an excellent candidate materials system, InGaN, whose band gap can be adjusted from 0.7 eV to 3.4 eV as the indium content is reduced. Recent progress has resulted in InGaN solar cells with 97% internal quantum efficiency and 57% external quantum efficiency with an active region only 60 nm thick. This work demonstrates that electron-hole pairs are very efficiently collected in InGaN materials and the absorption is very strong at the band gap. The toughness of the nitride materials translates into its excellent performances under harsh environments: high temperature and humidity and high concentration. Georgia Tech-CNRS and their partners have developed unique lift-off technologies that dramatically lower nitride cost as a result of the ability to reuse the substrates used for the growth of nitrides. These lift-off technologies are also favorable for integration of InGaN cells with building materials like glass or metal, or with other solar cells, such as those made of silicon. In this presentation InGaN solar cells progress and results will be presented.