Yan Danni,Dong Yuhui,Wei Naiwei,Yang Shuai,Zhu Hong,Gu Wanzhong,Zou Yousheng,Zeng Haibo
Quaternary Ag-In-Ga-S (AIGS) quantum dot (QD) is considered a promising, spectral-tunable, and environmentally friendly luminescent display material. However, the more complex surface defect states of AIGS QDs resulting from the coexistence of multiple elements lead to a low (< 60%) photoluminescence quantum yield (PLQY). Here, we develop a novel convenient method to introduce Z-type ligands ZnX 2 (X = Cl, Br, I) for passivating the surface defects of AIGS QDs to dramatically enhance the PLQY and stability without affecting the crystalline structure and morphology. Results show that the addition of ZnCl 2 during the purified process of AIGS QDs leads to a 3-fold increase of PLQY (from 28.5% to 87%). Impressively, the highest PLQY is up to a recorded value of 92%, which is comparable to typical heavy metal QDs. Exciton dynamics studies have shown that the rapid annihilation process of excitons in treated QDs is inhibited. We also confirm that the improvement in PLQY is a result of the effective passivation of the non-coordinating atom on the QD surface by building a new bonding between sulfur dangling and Zn 2+ . The realization of high PLQY will further promote the application of AIGS QDs in luminescent displays.
The control of surface properties of all inorganic cesium lead halide perovskite (CsPbX3; X = Cl, Br, or I) quantum dots (QDs) is essential to achieve excellent stability and high photoluminescence quantum yields (PLQYs). Herein, a facile method was performed to simultaneously enhance the stability and PLQYs of CsPbX3 QDs by a ZnX2/hexane solution post-treatment. We show that the halogen defect on the surface of CsPbX3 QDs can be treated in a controlled way, whereby the “black dots” that adhered on the surface as observed by transmission electron microscopy have be completely removed, resulting in enhanced stability and photoluminescence. The PLQYs of CsPbCl3, CsPbBr3, and CsPbI3 increased from 4, 58, and 63% to 86, 93, and 95%, respectively, and the origin of the “black dots” as well as their transformation mechanism has been demonstrated. As a result, the poly(dimethylsiloxane) composite films created by encapsulating stable and nearly defect-free green-emitting CsPbBr3, the red-emitting K2SiF6:Mn4+ phosphor, and a blue emission GaN chip were prepared and used to fabricate a remote-type white light-emitting diode device, which exhibits a high luminescence efficiency (≤98 lm/W) and a wide color gamut (∼130% of the National Television Standard Committee standard), suggesting the potential for liquid crystal display backlight application.
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