Hou Xiaoqi, Qin Haiyan, Peng Xiaogang
Key Laboratory of Excited-State Materials of Zhejiang Province, and Department of Chemistry, Zhejiang University, Hangzhou, 310027, P. R. China.
Key Laboratory of Intelligent Sensing Materials and Chip Integration Technology of Zhejiang Province, Hangzhou Innovation Institute, Beihang University, Hangzhou, 310051, P.R. China.
Nano Lett. 2021 May 12;21(9):3871-3878. doi: 10.1021/acs.nanolett.1c00396. Epub 2021 May 3.
Auger recombination is the main nonradiative process in multicarrier states of high-quality quantum dots (QDs). For the most-studied CdSe/CdS core/shell QDs, we effectively reduce the biexciton Auger rate by enhancing dielectric screening of band-edge carriers via epitaxial growth of additional ZnS shells. Super volume scaling of negative-trion Auger lifetime for CdSe/CdS core/shell QDs is achieved with the outermost ZnS shells. The volume of CdSe/CdS/ZnS QDs can be less than half that of CdSe/CdS QDs with the same negative-trion Auger lifetime. Auger suppression by the ZnS shells is more pronounced for QDs with wave functions of band-edge carriers spreading close to the inorganic-organic interface, such as CdSe/CdS QDs with small cores. A maximum drop of biexciton Auger rate of ∼50% and a maximum enhancement of biexciton emission quantum yield of 75% are achieved. Auger engineering by dielectric screening opens up new opportunities to improve the emission properties of multicarrier states in QDs.
俄歇复合是高质量量子点（QD）多载流子态中的主要非辐射过程。对于研究最多的CdSe/CdS核壳量子点，我们通过额外生长ZnS壳层来增强带边载流子的介电屏蔽，从而有效降低双激子俄歇复合率。通过最外层的ZnS壳层实现了CdSe/CdS核壳量子点负三激子俄歇寿命的超体积标度。在相同的负三激子俄歇寿命下，CdSe/CdS/ZnS量子点的体积可以小于CdSe/CdS量子点体积的一半。对于带边载流子波函数在无机-有机界面附近扩展的量子点，如小核的CdSe/CdS量子点，ZnS壳层对俄歇复合的抑制更为明显。双激子俄歇复合率最大下降约50%，双激子发射量子产率最大提高75%。通过介电屏蔽进行俄歇工程为改善量子点中多载流子态的发射特性开辟了新的机会。
