In-depth profiling of non-radiative carrier recombination in the multi-junction solar cells by using the photothermal spectroscopy

基于光热光谱的信号产生和传播原理，我们发展了检测多结太阳电池中光生载流子非辐射复合损耗的深度剖析技术。将频率相关的压电光热(PPT)测量应用于多量子井(MQW)结构插入p-i-n GaAs太阳电池后，即使在高频测量条件下，我们也检测到来自MQW的PPT信号。当频率较高时，由于热扩散长度的减小，在MQW区域内产生的PPT信号预计将呈指数下降。目前的实验结果清楚地表明，MQW中的光生载流子可以热逃逸，室温下的载流子收集效率得到了显着提高。

Based on the signal generation and propagation principle of the photothermal spectroscopy, we have developed the in-depth profiling technique that detects the non-radiative recombination loss of photo-generated carriers in the multi-junction solar cells. After applying the frequency-dependent piezoelectric photothermal (PPT) measurements to the multi-quantum well (MQW) structure inserted p-i-n GaAs solar cells, we detected the PPT signals originating from MQWs even in the high frequency measuring conditions. When higher frequency, the PPT signals generated within the MQW region are expected to exponentially decrease because of decreasing the thermal diffusion length. Present experimental results show clearly that photo-generated carries in MQW can thermally escape and the carrier collection efficiency at room temperature is significantly improved.