InGaN／GaN多量子阱太阳电池的研制及特性研究

Fabrication and Performance of InGaN/GaN MQWs Solar Cell

利用金属有机物化学气相沉积技术在蓝宝石衬底上生长了InGaN/GaN多量子阱外延结构,高分辨率X射线衍射测量结果显示,量子阱结构界面清晰,周期重复性很好,InGaN阱层的In组分约为0.2。利用该外延结构制备的InGaN/GaN多量子阱太阳电池的开路电压为2.16V,转换效率达到了0.64%。器件的I-V测量结果显示,在光照条件下,曲线的正向区域存在一明显的"拐点"。随着聚光度的减小,I-V曲线的"拐点"逐渐向高电压区域移动,同时器件的开路电压也随之急剧下降。通过与理论计算对比,发现器件开路电压的下降幅度明显大于理论计算值。进一步分析表明,InGaN量子阱的极化效应不仅是I-V曲线产生拐点以及器件开路电压下降过快的主要原因,也是影响氮化物太阳电池性能的关键因素之一。

InGaN/GaN multiple quantum wells （MQWs） epitaxial structures were grown by metalorganic chemical vapor deposition （MOCVD） on sapphire substrate. The result of high- resolution X-ray diffraction indicates abrupt interface and good layer periodicity in MQWs. The In content in InGaN layer is estimated to be 0.2. The open voltage and the conversion efficiency of the fabricated InGaN/GaN MQWs solar cells are measured to be 2. 16 V and 0. 64%, respectively. The current-voltage （I-V） characteristics under illumination show that there is a distinct ＂turning point＂ in the positive area of the I-V curve. With reduction of the concentration ratio, the ＂turning point＂ gradually moves to the high-voltage area and the open voltage simultaneously drops rapidly. By comparing the theoretical and experimental results, it can be found that the measured results drop significantly greater than the calculated ones. Further analysis reveals that the polarization effect of InGaN/GaN MQWs is the main cause of the ＂turning point＂ in I-V curve and the fast drop of open voltage. It is also one of the key factors affecting the performance of nitride solar cells.