Department of Chemistry and School of Energy Resources, University of Wyoming, Laramie, WY 80271, USA.
Science. 2010 Oct 1;330(6000):63-6. doi: 10.1126/science.1191462.
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.
多激子产生，即一个高能光子产生两个电子-空穴对，在体半导体中已经得到很好的确立，但在像半导体纳米晶体这样的量子限制系统中，对这种效应的效率的评估仍然存在争议。我们使用由化学结合到 TiO(2)单晶上的 PbS 纳米晶体组成的光电化学系统，证明了光电流的收集，其量子产率大于每个光子一个电子。PbS 纳米晶体和体 TiO(2)之间强的电子耦合和有利的能级排列促进了多激子的提取，比它们的复合更快，同时也从更高的量子点激发态收集热电子。我们的结果对提高光伏器件的效率具有重要意义，因为它避免了由于光生载流子的热化而导致的损耗。
