Cover Picture: Properties of nitride-based photovoltaic cells under concentrated light illumination (Phys. Status Solidi RRL 4/2012)
Shota Yamamoto, Mikiko Mori, Yosuke Kuwahara, Takahiro Fujii, Tatsuo Nakao, Shinichiro Kondo, Motoaki Iwaya, Tetsuya Takeuchi, Satoshi Kamiyama, Isamu Akasaki and Hiroshi Amano
Version of Record online: 29 MAR 2012 | DOI: 10.1002/pssr.201290006
One of the disadvantages of compound semiconductor solar cells is their high cost compared with silicon or organic solar cells. This problem can be solved by using a condenser lens system. Thus, if the solar cells can operate at 200 suns, the cost per chip would be reduced considerably. In their Letter on pp. 145–147, Yamamoto et al. report on the focusing properties of nitride-based solar cells up to 200 suns and also discuss the dependence of solar cell characteristics on concentration ratio. The structure of the devices prepared in this study consists of 50 pairs of unintentionally doped Ga0.83In0.17N/Ga0.93In0.07N superlattice layers as active layers on freestanding GaN substrate. Another 10 pairs of Si-doped Ga0.90In0.10N/GaN superlattice layers were inserted beneath the active layers in order to reduce the dislocation density. These nitride-based solar cells operate effectively even at 200 suns, their conversion efficiency of 3.4% is the highest ever reported value for nitride solar cells.