School of Photovoltaic and Renewable Energy Engineering, UNSW Sydney, Sydney, NSW 2052, Australia.
Nanoscale. 2017 Nov 9;9(43):17133-17142. doi: 10.1039/c7nr05247b.
The carrier dynamics of lead sulphide quantum dot (PbS QD) drop cast films and closely packed ordered Langmuir-Blodgett films are studied with ultra-fast femtosecond transient absorption spectroscopy. The photo-induced carrier temperature is extracted from transient absorption spectra and monitored as a function of time delay. The cooling dynamics of carriers in PbS QDs suggest a reduction of the carrier energy loss rate at longer time delays through the retardation of the longitudinal optical (LO) phonon decay due to partial heating of acoustic phonon modes. A slowed hot carrier cooling time up to 116 ps is observed in the drop cast film. A faster cooling rate was also observed in the highly compact Langmuir-Blodgett film due to the enhanced carrier-LO phonon coupling strength arising from the Coulombic interaction in neighboring QDs, which is verified by temperature dependent steady state PL measurements.
采用超快飞秒瞬态吸收光谱研究了硫化铅量子点（PbS QD）滴铸薄膜和紧密堆积有序Langmuir-Blodgett 薄膜的载流子动力学。从瞬态吸收光谱中提取光致载流子温度，并作为时间延迟的函数进行监测。PbS QD 中载流子的冷却动力学表明，通过延迟长光学（LO）声子衰减，部分加热声子模式，在较长的时间延迟下，载流子能量损失率降低。在滴铸薄膜中观察到高达 116 ps 的热载流子冷却时间延长。在高度致密的 Langmuir-Blodgett 薄膜中，由于相邻 QD 中的库仑相互作用增强了载流子-LO 声子耦合强度，也观察到更快的冷却速率，这可以通过温度相关的稳态 PL 测量来验证。
