Department of Materials Science and Engineering , Hongik University , Seoul 04066 , Korea.
ACS Appl Mater Interfaces. 2019 Feb 27;11(8):8250-8257. doi: 10.1021/acsami.8b20894. Epub 2019 Feb 13.
On the basis of bluish-emitting double-shelled quantum dots (QDs) of Zn-Cu-Ga-S (ZCGS)/ZnS/ZnS, Mn doping into ZCGS host with different Mn/Cu concentrations is implemented via surface adsorption and lattice diffusion. The resulting double-shelled Mn-doped ZCGS (ZCGS/Mn) QDs exhibit a distinct MnT-A emission as a consequence of effective lattice incorporation simultaneously with host intragap states-involving emissions of free-to-bound and donor-acceptor pair recombinations. The relative contribution of Mn emission to the overall photoluminescence (PL) is consistently proportional to its concentration, resulting in tunable PL from bluish, white, to reddish white. Regardless of Mn doping and its concentration, all QDs possess high PL quantum yield levels of 74-79%. Those undoped and doped QDs are then employed as an emitting layer (EML) of all-solution-processed QD-light-emitting diodes (QLEDs) with hybrid charge transport layers and their electroluminescence (EL) is compared. Compared to undoped QDs, doped analogues give rise to a huge spectral disparity of EL versus PL, specifically showing a near-complete quenching of Mn EL. This unexpected observation is rationalized primarily by considering unbalanced carrier injection to QD EML on the basis of energetic alignment of the present QLED and rapid trapping of holes injected at intragap states of QDs.
在 Zn-Cu-Ga-S（ZCGS）/ZnS/ZnS 蓝色发射双层量子点的基础上，通过表面吸附和晶格扩散，在不同 Mn/Cu 浓度的 ZCGS 宿主中掺杂 Mn。所得双层 Mn 掺杂 ZCGS（ZCGS/Mn）量子点由于晶格有效掺入同时涉及自由-束缚和施主-受主对复合的能带内态发射，表现出明显的 MnT-A 发射。Mn 发射对总光致发光（PL）的相对贡献与其浓度成正比，导致从蓝色、白色到红白色可调的 PL。无论是否掺杂 Mn 及其浓度如何，所有量子点都具有 74-79%的高 PL 量子产率水平。然后将未掺杂和掺杂的量子点用作全溶液处理量子点发光二极管（QLED）的发射层（EML），采用混合电荷传输层，并对其电致发光（EL）进行比较。与未掺杂的量子点相比，掺杂的类似物导致 EL 与 PL 之间存在巨大的光谱差异，特别是 Mn EL 几乎完全猝灭。这种意外的观察主要通过考虑基于本 QLED 的能量排列和量子点能带内态中注入空穴的快速俘获的 QD EML 中载流子注入的不平衡来合理化。
