Influence of InGaN/GaN multiple quantum well structure on photovoltaic characteristics of solar cell

摘要

We have investigated InGaN/GaN multiple quantum well (MQW) solar cells in terms of the relationship between the short-circuit current and the MQW structure. We previously reported that higher short-circuit current is obtained in solar cells with thinner GaN barrier layers, and in this investigation, we also obtained higher short-circuit current in solar cells with higher numbers of InGaN/GaN periodic layers. These results can be explained by the hypothesis that the transport characteristics of photoinduced carriers are characterized by the specific length within which carriers photoinduced in the InGaN well layer can move before recombination. The carrier collection efficiency is improved by the drift in the barrier layer due to the forward internal electric field and degraded by the carrier accumulation in the well layer caused by the inverse internal electric field and the potential barrier between layers, which well describes the influence of the MQW structure on the specific length. Using this model, we discuss how we can determine the MQW structure that yields higher short-circuit current, and conclude that the optimum thickness of the InGaN well layer is about 2-3 nm when the thickness of the GaN barrier layer is 3-8 nm.