具有 Mn 离子作为激子耦合剂的 Mn 掺杂 CdS/ZnSe/ZnS 量子点的亮型-II 光致发光。

Bright type-II photoluminescence from Mn-doped CdS/ZnSe/ZnS quantum dots with Mn ions as exciton couplers.

机构信息

Advanced Photonic Center, Southeast University, Nanjing 210096, China.

出版信息

Nanoscale. 2017 Nov 30;9(46):18281-18289. doi: 10.1039/c7nr05670b.

Abstract

Mn ions were introduced as exciton couplers to enhance the quantum yield (QY) of type-II photoluminescence (PL) from CdS/ZnSe/ZnS quantum dots (QDs) with slow hot-exciton cooling and low radiative rate. Transient absorption spectroscopy verifies the faster bleach recovery and faster peak red-shifting at the charge-transfer state. And the transient PL peak of the QDs changes from blue-shifting to red-shifting due to Mn doping. The QY of type-II PL can be enhanced from ∼35% to ∼60% by Mn doping. As the energy-transfer-stations of hot excitons during rapid ET (∼100 ps), Mn ions transform more excitons from hot to cold for emission. As the couplers of cold excitons during long thermal equilibrium (∼100 ns), Mn ions further decrease exciton trapping by strong bidirectional coupling. This work provides a unique way of acquiring high QY of type-II PL, and highlights the general law of PL enhancement in Mn-doped QDs.

摘要

锰离子被引入作为激子耦合剂，以提高具有慢热激子冷却和低辐射速率的 II 型光致发光（PL）的量子产率（QY）从 CdS/ZnSe/ZnS 量子点（QDs）。瞬态吸收光谱证实了更快的漂白恢复和更快的电荷转移态的峰值红移。并且由于 Mn 掺杂，QD 的瞬态 PL 峰从蓝移变为红移。通过 Mn 掺杂，II 型 PL 的 QY 可以从约 35%增强到约 60%。作为快速 ET（约 100 ps）期间热激子的能量转移站，Mn 离子将更多的激子从热激子转化为冷激子以发射。作为长热平衡（约 100 ns）期间冷激子的耦合剂，Mn 离子通过强双向耦合进一步减少激子俘获。这项工作提供了一种获得高 II 型 PL 的量子产率的独特方法，并突出了 Mn 掺杂 QD 中 PL 增强的一般规律。