Electrically active defects present in three InAs/GaAs quantum dots (QDs) intermediate band solar cells grown by metalorganic vapor phase epitaxy have been investigated. The devices' structures are almost identical, differing only in the growth temperature and thickness of the GaAs layers that cover each InAs QD layer. These differences induce significant changes in the solar energy conversion efficiency of the photovoltaic cells, as previously reported. In this work, a systematic investigation was carried out using deep level transient spectroscopy (DLTS) and Laplace DLTS measurements on control samples and solar cell devices, which have clearly shown that electrically active traps play an important role in the device figures of merit, such as open circuit voltage, short circuit current, and shunt resistance. In particular, it was found that the well-known EL2 defect negatively affects both the open circuit voltage and shunt resistance, more in structures containing QDs, as a consequence of the temperature cycle required to deposit them. Other unidentified defects, that are absent in samples in which the QDs were annealed at 700 °C, contribute to a reduction of the short circuit current, as they increase the Shockley-Read-Hall recombination. Photoluminescence results further support the DLTS-based assignments.

中文翻译：

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缺陷对量子点中带太阳能电池性能的作用


研究了通过金属有机气相外延生长的三种 InAs/GaAs 量子点 (QD) 中带太阳能电池中存在的电活性缺陷。这些器件的结构几乎相同，只是生长温度和覆盖每个 InAs QD 层的 GaAs 层的厚度不同。正如之前报道的，这些差异导致光伏电池的太阳能转换效率发生显着变化。在这项工作中，使用深能级瞬态光谱（DLTS）和拉普拉斯 DLTS 测量对对照样品和太阳能电池器件进行了系统研究，清楚地表明电活性陷阱在器件品质因数中发挥着重要作用，例如如开路电压、短路电流和分流电阻。特别是，我们发现众所周知的 EL2 缺陷会对开路电压和分流电阻产生负面影响，尤其是在包含 QD 的结构中，这是由于沉积 QD 所需的温度循环造成的。量子点在 700 °C 下退火的样品中不存在其他未识别的缺陷，这些缺陷有助于减少短路电流，因为它们会增加肖克利-雷德-霍尔复合。光致发光结果进一步支持基于 DLTS 的分配。