| Summary: | 碩士 === 國立臺灣大學 === 光電工程學研究所 === 100 === Indium gallium nitride (InGaN) is a promising material for photovoltaic devices due to it potential to realize nearly full absorption of solar spectrum. A challenge for InGaN-based solar cells is the deteriorated crystal qualities at high indium (In) contents. In this thesis, severe In fluctuation is observed in InxGa1-xN/GaN multiple quantum well (MQW) solar cells for x = 0.3 using scanning transmission electron microscopy. The strong fluctuation and sacrificed crystal qualities lead to unsatisfactory photovoltaic performances. A strong temperature-dependent characteristic is observed for the device and is attributed to the photocurrents thermally activated from the shallow QWs.
In order to enhance the conversion efficiency (η), zinc oxide (ZnO) nanorod arrays (NRAs) are applied as the antireflection (AR) coating on InGaN/GaN MQW solar cells. The NRAs are synthesized by a cost-effective hydrothermal method. The length of NRAs plays an important role in photovoltaic characteristics considering the trade-off between AR performances and bandgap absorption of ZnO. In addition, the syringe-like ZnO NRAs possessing superior advantages to the flat-top ZnO NRAs are also applied as the light-harvesting layer, resulting in the improvement of 36 % from that obtained on the solar cells with bare surface.
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