Yumoto Go, Tahara Hirokazu, Kawawaki Tokuhisa, Saruyama Masaki, Sato Ryota, Teranishi Toshiharu, Kanemitsu Yoshihiko
Institute for Chemical Research , Kyoto University , Uji , Kyoto 611-0011 , Japan.
J Phys Chem Lett. 2018 May 3;9(9):2222-2228. doi: 10.1021/acs.jpclett.8b01029. Epub 2018 Apr 17.
Combining the superior optical properties of their bulk counterparts with quantum confinement effects, lead halide perovskite nanocrystals are unique laser materials with low-threshold optical gain. In such nonlinear optical regimes, multiple excitons are generated in the nanocrystals and strongly affect the optical gain through many-body interactions. Here, we investigate the exciton-exciton interactions in CsPbI nanocrystals by femtosecond transient absorption spectroscopy. From the analysis of the induced absorption signal observed immediately after the pump excitation, we estimated the binding energy for the hot biexcitons that are composed of an exciton at the band edge and a hot exciton generated by the pump pulse. We found that the exciton-exciton interaction becomes stronger for hot excitons with greater excess energies and that the optical gain can be controlled by changing the excess energy of the hot excitons.
卤化铅钙钛矿纳米晶体将其块体材料的优异光学性质与量子限制效应相结合，是具有低阈值光学增益的独特激光材料。在这种非线性光学体系中，纳米晶体内会产生多个激子，并通过多体相互作用强烈影响光学增益。在此，我们通过飞秒瞬态吸收光谱研究了CsPbI纳米晶体中的激子 - 激子相互作用。通过对泵浦激发后立即观察到的诱导吸收信号进行分析，我们估算了由带边激子和泵浦脉冲产生的热激子组成的热双激子的结合能。我们发现，对于具有更高过剩能量的热激子，激子 - 激子相互作用变得更强，并且可以通过改变热激子的过剩能量来控制光学增益。
