Department of Chemistry, University of Washington, Seattle, Washington 98195-1700, United States.
ACS Nano. 2011 May 24;5(5):4158-68. doi: 10.1021/nn200889q. Epub 2011 Apr 11.
Auger processes in colloidal semiconductor nanocrystals have been scrutinized extensively in recent years. Whether involving electron-exciton, hole-exciton, or exciton-exciton interactions, such Auger processes are generally fast and hence have been considered prominent candidates for interpreting fast processes relevant to photoluminescence blinking and multiexciton decay. With recent advances in the chemistries of nanocrystal doping, increasing attention is now being paid to analogous photophysical properties of colloidal-doped semiconductor nanocrystals. Here, we report the first investigation of the effects of electron-dopant exchange interactions on dopant luminescence in doped semiconductor nanocrystals. Using electrochemical techniques, electrical control of charge-carrier densities in films of colloidal Mn(2+)-doped CdS quantum dots has been achieved and used to demonstrate remarkably effective Auger de-excitation of photoexcited Mn(2+). The doped nanocrystals are found to be substantially more sensitive to Auger de-excitation than their undoped analogues, a result shown to arise primarily from the long Mn(2+) excited-state lifetime. This observation of exceptionally effective Auger quenching has broader implications in areas of high-power, single-particle, or electrically driven luminescence of doped semiconductor nanocrystals, and also suggests interesting opportunities for modulating Mn(2+) photoluminescence intensities on sublifetime time scales, or for imaging charge carriers in nanocrystal-based devices.
近年来，胶体半导体纳米晶体中的俄歇过程受到了广泛的关注。无论是涉及电子-激子、空穴-激子还是激子-激子相互作用，这种俄歇过程通常都很快，因此被认为是解释与光致发光闪烁和多激子衰减相关的快速过程的突出候选者。随着纳米晶掺杂化学的最新进展，人们越来越关注胶体掺杂半导体纳米晶体的类似光物理性质。在这里，我们报告了对电子掺杂剂交换相互作用对掺杂半导体纳米晶体中掺杂剂发光影响的首次研究。使用电化学技术，已经实现了胶体 Mn(2+)-掺杂 CdS 量子点薄膜中载流子密度的电控制，并利用该技术证明了光激发 Mn(2+)的显著有效的俄歇退激发。研究发现，掺杂纳米晶体比未掺杂的类似物对俄歇退激发更为敏感，这一结果主要归因于 Mn(2+)激发态的长寿命。这种对异常有效的俄歇猝灭的观察在掺杂半导体纳米晶体的高功率、单粒子或电驱动发光等领域具有更广泛的意义，并且还为在亚寿命时间尺度上调制 Mn(2+)光致发光强度或对基于纳米晶体的器件中的载流子进行成像提供了有趣的机会。
