Babentsov V, Riegler J, Schneider J, Fiederle M, Nann T
Freiburger Materialforschungszentrum, Albert-Ludwigs-Universität Freiburg, Stefan-Meier-Strasse 21, D-79104 Freiburg, Germany.
J Phys Chem B. 2005 Aug 18;109(32):15349-54. doi: 10.1021/jp052229c.
The excitonic and deep-level photoluminescence (PL) in CdSe nanocrystal (NC) films (wurtzite type) was studied under continuous-wave excitation as a function of excitation power, temperature, and time of photoaging. It was shown that the intensity-power dependencies are identical for excitonic and deep-level emissions in a wide temperature range. At low temperatures (80-100 K), both emissions were saturated at the laser power used, which generates more than one exciton per nanocrystal. A transition point from the linear to the saturated region was dependent on the temperature, size, and quality of the NCs. A clear inverse dependency between the intensities of excitonic and deep-level emissions was revealed at 80 K over the entire sample area. At room-temperature, the quantum yield dropped significantly and a higher laser power was needed to reach PL saturation. An increase in temperature led to worsening of the reverse dependence between excitonic and deep-level emissions, and at room-temperature, they became uncorrelated. These results can be explained by Auger recombination and also by an increase of nonradiative recombination in the surface states with increasing temperature.
研究了纤锌矿型CdSe纳米晶体（NC）薄膜中的激子和深能级光致发光（PL），其作为连续波激发功率、温度和光老化时间的函数。结果表明，在很宽的温度范围内，激子和深能级发射的强度-功率依赖关系是相同的。在低温（80-100K）下，在所使用的激光功率下，两种发射均达到饱和，该激光功率在每个纳米晶体中产生不止一个激子。从线性区域到饱和区域的转变点取决于纳米晶体的温度、尺寸和质量。在80K下，在整个样品区域内，激子和深能级发射强度之间呈现出明显的反比关系。在室温下，量子产率显著下降，需要更高的激光功率才能达到PL饱和。温度升高导致激子和深能级发射之间的反向依赖关系变差，在室温下，它们变得不相关。这些结果可以用俄歇复合以及随着温度升高表面态中非辐射复合的增加来解释。
