Department of Chemistry, McGill University, Montreal, Quebec H3A 0G4, Canada.
J Chem Phys. 2023 Apr 21;158(15). doi: 10.1063/5.0142113.
We monitor the time-resolved photoluminescence (t-PL) from CsPbBr3 perovskite nanocrystals with a time resolution of 3 ps, which is fast enough to resolve emission from potential multiexcitonic states. Being 15 nm in length and twice the Bohr length, these nanocrystals are either weakly confined or bulk-like. In contrast to this expectation of weak confinement, emission from multiexcitons is observed with binding energies consistent with strongly confined quantum dots. In addition to emission from biexcitons, emission from triexcitons is observed. The triexciton emission includes both S and P recombination channels. Excitation with different amounts of excess energy yields the same PL spectral dynamics, indicating that there are no hot carrier effects, and the electronic structure of the absorbing states is the same. The kinetics of the multiexciton populations are presented in two ways. The kinetics are first shown in a spectrally integrated form, showing faster t-PL at higher fluences independent of excitation excess energy. Both excess energies show the same saturation response. In the second way of presenting the kinetics, the multiexciton populations are decomposed and presented as transients and saturation curves. These decomposed spectra into exciton, biexciton, and triexciton populations enable further insight into their kinetics and fluence dependence.
我们使用时间分辨率为 3 ps 的时间分辨光致发光 (t-PL) 监测 CsPbBr3 钙钛矿纳米晶体，其时间分辨率足够快，可以分辨潜在的多激子态的发射。这些纳米晶体长 15nm，是玻尔半径的两倍，其具有弱限域或体相特征。与弱限域的预期相反，观察到了多激子的发射，其结合能与强限域的量子点一致。除了双激子的发射外，还观察到了三激子的发射。三激子的发射包括 S 和 P 复合通道。用不同量的过剩能量进行激发会产生相同的 PL 光谱动力学，这表明没有热载流子效应，并且吸收态的电子结构是相同的。多激子群体的动力学以两种方式呈现。动力学首先以光谱积分的形式呈现，显示出在更高的光强下具有更快的 t-PL，与激发过剩能量无关。两种过剩能量都显示出相同的饱和响应。在呈现动力学的第二种方式中，将多激子群体分解并呈现为瞬态和饱和曲线。这些分解为激子、双激子和三激子群体的光谱使我们能够进一步了解它们的动力学和光强依赖性。
