Multiple Exciton Collection in a Sensitized Photovoltaic System
Multiple Exciton Collection in a Sensitized Photovoltaic System
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DOI：
10.1126/science.1191462
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发表时间：
2010-10-01
期刊：
影响因子：
56.9
通讯作者：
Parkinson, B. A.
中科院分区：
文献类型：
--
作者：
Sambur, Justin B.;Novet, Thomas;Parkinson, B. A.
多激子产生，即由一个高能光子产生两个电子-空穴对，在块状半导体中已经很好地建立起来了，但在半导体纳米晶体等量子受限系统中，对这种效应效率的评估仍然存在争议。我们使用了一个由化学结合到TiO(2)单晶的PbS纳米晶体组成的光电化学系统来证明光电流的收集，其量子产率大于每个光子一个电子。PbS纳米晶体与体TiO(2)之间的强电子耦合和有利的能级排列有利于比它们重组更快地提取多个激子，以及从更高量子点激发态收集热电子。我们的研究结果对提高光电器件的效率具有重要意义，因为它可以避免由于光生载流子的热化而造成的损耗。
Multiple exciton generation, the creation of two electron-hole pairs from one high-energy photon, is well established in bulk semiconductors, but assessments of the efficiency of this effect remain controversial in quantum-confined systems like semiconductor nanocrystals. We used a photoelectrochemical system composed of PbS nanocrystals chemically bound to TiO(2) single crystals to demonstrate the collection of photocurrents with quantum yields greater than one electron per photon. The strong electronic coupling and favorable energy level alignment between PbS nanocrystals and bulk TiO(2) facilitate extraction of multiple excitons more quickly than they recombine, as well as collection of hot electrons from higher quantum dot excited states. Our results have implications for increasing the efficiency of photovoltaic devices by avoiding losses resulting from the thermalization of photogenerated carriers.