Gogoi Hemen, Pathak Sushil Swaroop, Dasgupta Souradip, Panchakarla Leela Srinivas, Nath Sukhendu, Datta Anindya
Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai 400076, India.
Radiation & Photochemistry Division, Bhabha Atomic Research Centre, Mumbai 400 085, India.
J Phys Chem Lett. 2022 Jul 19:6770-6776. doi: 10.1021/acs.jpclett.2c01623.
CdS quantum dots (QDs), synthesized by a sol-gel method, exhibit significantly Stokes shifted bright photoluminescence (PL), predominantly from the trap states. Surprisingly, the PL decay at the emission maximum is single-exponential. This is an unusual observation for as-prepared QDs and indicates a narrow distribution in the nature of trap states. A closer look reveals an additional fast component for the decays at shorter emission wavelengths, presumably due to the band edge emission, which remains elusive in the steady-state spectra. Indeed, a significantly narrower and blue-shifted emission band is observed in the decay-associated spectra. The contribution of this component to the steady-state PL intensity is shown to be overwhelmed by that of the significantly stronger trap emission. Exciton dynamics in the quantum dots is elucidated using transient absorption spectra, in which the stimulated emission is observed even at low pump power.
通过溶胶 - 凝胶法合成的硫化镉量子点（QDs）表现出显著的斯托克斯位移明亮光致发光（PL），主要来自陷阱态。令人惊讶的是，在发射最大值处的PL衰减是单指数的。对于制备好的量子点来说，这是一个不寻常的观察结果，表明陷阱态的性质分布狭窄。进一步观察发现，在较短发射波长处的衰减存在一个额外的快速成分，可能是由于带边发射，这在稳态光谱中仍然难以捉摸。实际上，在与衰减相关的光谱中观察到一个明显更窄且蓝移的发射带。结果表明，该成分对稳态PL强度的贡献被明显更强的陷阱发射所掩盖。利用瞬态吸收光谱阐明了量子点中的激子动力学，其中即使在低泵浦功率下也能观察到受激发射。
