Cirloganu Claudiu M, Padilha Lazaro A, Lin Qianglu, Makarov Nikolay S, Velizhanin Kirill A, Luo Hongmei, Robel Istvan, Pietryga Jeffrey M, Klimov Victor I
Center for Advanced Solar Photophysics, Los Alamos National Laboratory, Los Alamos, New Mexico 87544, USA.
Department of Chemical Engineering, New Mexico State University, Las Cruces, New Mexico 88003, USA.
Nat Commun. 2014 Jun 18;5:4148. doi: 10.1038/ncomms5148.
One process limiting the performance of solar cells is rapid cooling (thermalization) of hot carriers generated by higher-energy solar photons. In principle, the thermalization losses can be reduced by converting the kinetic energy of energetic carriers into additional electron-hole pairs via carrier multiplication (CM). While being inefficient in bulk semiconductors this process is enhanced in quantum dots, although not sufficiently high to considerably boost the power output of practical devices. Here we demonstrate that thick-shell PbSe/CdSe nanostructures can show almost a fourfold increase in the CM yield over conventional PbSe quantum dots, accompanied by a considerable reduction of the CM threshold. These structures enhance a valence-band CM channel due to effective capture of energetic holes into long-lived shell-localized states. The attainment of the regime of slowed cooling responsible for CM enhancement is indicated by the development of shell-related emission in the visible observed simultaneously with infrared emission from the core.
限制太阳能电池性能的一个过程是由高能太阳光子产生的热载流子的快速冷却（热化）。原则上，通过载流子倍增（CM）将高能载流子的动能转化为额外的电子-空穴对，可以减少热化损失。虽然在体半导体中这个过程效率不高，但在量子点中会增强，不过还不足以显著提高实际器件的功率输出。在这里，我们证明厚壳PbSe/CdSe纳米结构的CM产率比传统的PbSe量子点几乎提高了四倍，同时CM阈值也显著降低。由于高能空穴有效地捕获到长寿命的壳层局域态中，这些结构增强了价带CM通道。与来自核心的红外发射同时观察到的可见光谱中壳层相关发射的出现，表明达到了导致CM增强的慢冷却状态。
