Chuang Chia-Hao Marcus, Maurano Andrea, Brandt Riley E, Hwang Gyu Weon, Jean Joel, Buonassisi Tonio, Bulović Vladimir, Bawendi Moungi G
†Department of Materials Science and Engineering, ‡Department of Electrical Engineering and Computer Science, §Department of Mechanical Engineering, and ∥Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States.
Nano Lett. 2015 May 13;15(5):3286-94. doi: 10.1021/acs.nanolett.5b00513. Epub 2015 Apr 30.
Quantum dot photovoltaics (QDPV) offer the potential for low-cost solar cells. To develop strategies for continued improvement in QDPVs, a better understanding of the factors that limit their performance is essential. Here, we study carrier recombination processes that limit the power conversion efficiency of PbS QDPVs. We demonstrate the presence of radiative sub-bandgap states and sub-bandgap state filling in operating devices by using photoluminescence (PL) and electroluminescence (EL) spectroscopy. These sub-bandgap states are most likely the origin of the high open-circuit-voltage (VOC) deficit and relatively limited carrier collection that have thus far been observed in QDPVs. Combining these results with our perspectives on recent progress in QDPV, we conclude that eliminating sub-bandgap states in PbS QD films has the potential to show a greater gain than may be attainable by optimization of interfaces between QDs and other materials. We suggest possible future directions that could guide the design of high-performance QDPVs.
量子点光伏器件（QDPV）为低成本太阳能电池提供了潜力。为了制定持续改进QDPV的策略，深入了解限制其性能的因素至关重要。在此，我们研究了限制PbS QDPV功率转换效率的载流子复合过程。我们通过光致发光（PL）和电致发光（EL）光谱证明了在工作器件中存在辐射子带隙态和子带隙态填充。这些子带隙态很可能是迄今为止在QDPV中观察到的高开路电压（VOC）损失和相对有限的载流子收集的根源。将这些结果与我们对QDPV近期进展的观点相结合，我们得出结论，消除PbS量子点薄膜中的子带隙态可能比通过优化量子点与其他材料之间的界面获得更大的增益。我们提出了可能指导高性能QDPV设计的未来方向。
