Enhanced aqueous stability and radiative-charge-transfer of CsPbBr3/Ag2S perovskite nanocrystal hybrids
Graphical abstract
Introduction
CsPbX3 (X = Cl, Br, I) perovskite nanocrystals (PNCs) are promising candidates for solar cells [[1], [2], [3], [4]], light emitting diodes [[5], [6], [7], [8]], photodetectors [9], and other optoelectronic devices [10,11], due to their desirable optical characteristics of color tunability [5,12], monochromatic photoluminescence (PL) emission [13,14], and high PL quantum yield (QY) [15,16]. Although PNCs arouse tremendous interests in scientific communities [17], investigation and application of them are still seriously hindered by their poor stability to moisture [7,18]. Several strategies have been tested to improve the aqueous stability of PNCs. One is to isolate PNCs from moisture via coating them with inert and/or hydrophobic materials [19,20], such as silica [21,22] and polystyrene [23,24]. For example, embedding CsPbX3 PNCs in polystyrene microspheres can improve their aqueous stability for cell imaging [24]. Another approach is to increase the intrinsic stability of PNCs via doping heteroatoms [25,26], halide-rich syntheses [27,28], surface functionalization [29,30], and/or changing ligands [31,32]. Passivating CsPbBr3 PNCs surface with the silver complex can lead to enhanced photostability of CsPbBr3 PNCs [33]. Balakrishnan demonstrates that forming Au nanocrystals (NCs) on CsPbBr3 PNCs can bring out stable perovskite hybrids under ambient conditions [34], which opens a way towards stable PNCs via forming various hybrid nanostructures, such as CsPbBr3@Ag, CsPbBr3/ZnS, and CsPbBr3/PbSe [[35], [36], [37]]. Unfortunately, the stability of these PNCs hybrids against polar solvents is still intrinsically fragile [38].
Herein, a convenient and effective strategy for improved aqueous stability and radiative-charge-transfer of PNCs is proposed by anchoring Ag2S nanoparticles (NPs) onto CsPbBr3 PNCs via directly decomposing silver diethyldithiocarbamate (Ag(DDTC)) in the CsPbBr3 PNCs crude. The obtained CsPbBr3-Ag2S nano-heterostructures, i.e. PNCs hybrids, not only demonstrates dramatically enhanced aqueous stability up to 1 month and PLQY up to 82% in pure water, but also exhibits promoted electrochemical charge-injection response upon the assistant of Ag2S and boosted monochromatic electrochemiluminescence (ECL) than CsPbBr3 PNCs in aqueous electrolyte, as a result of the stronger electrochemical response of Ag2S than CsPbBr3 as well as the enhanced radiative charge recombination induced by transferring the charges injected onto the Ag2S segment into the CsPbBr3 segment. These findings promise both monochromatic electrochemiluminophores and perovskite heterostructures for stable and tunable optoelectronic devices [37,39].
Section snippets
Materials
All chemicals and reagents are of analytical grade or better, all aqueous solutions are prepared with DDW. Cesium carbonate (Cs2CO3, 99%), lead bromide (PbBr2, 99%), 1-octadecene (ODE, C18H36, 90%), oleic acid (OA, 90%), oleylamine (OAL, C18H37N, 80–90%), hexane (C6H14, 97%), and TPrA (>99%) are purchased from Aladdin. Silver diethyldithiocarbamate (Ag(DDTC), 99%) is obtained from Shanghai Titan Technology Co., Ltd. (Shanghai, China). Air-free supporting electrolyte solution is achieved by
Characterization of CsPbBr3 PNCs and CsPbBr3-Ag2S hybrids
As shown in Fig. 1a, both pure CsPbBr3 PNCs and CsPbBr3-Ag2S hybrids in hexane exhibit similar absorption nature with the first excitonic peak around 504 nm and high monochromatic PL nature with maximum emission around 515 nm and full width at half-maximum (FWHM) of 21 nm respectively. The formation of CsPbBr3-Ag2S hybrids via decomposing Ag(DDTC) in CsPbBr3 PNCs crude demonstrates negligible influence on the excited states for PL of CsPbBr3 PNCs. PLQY of CsPbBr3 PNCs and CsPbBr3-Ag2S hybrids
Conclusions
Hybriding CsPbBr3 PNCs with small bandgap Ag2S NPs can be conveniently achieved and bring out promising CsPbBr3-Ag2S hybrids with improved aqueous stability and radiative charge transfer for both PL and ECL. The electrons and/or holes injected onto the Ag2S segment of CsPbBr3-Ag2S hybrids can be transferred into the counterpart CsPbBr3 segment for enhanced radiative charge transfer occurred within the CsPbBr3 segment via some ways. ECL transient demonstrates that merely injecting holes onto
CRediT authorship contribution statement
Kena Fu:Conceptualization, Investigation, Writing - original draft.Yupeng He:Investigation, Formal analysis.Bin Zhang:Supervision.Xuwen Gao:Validation, Formal analysis.Guizheng Zou:Writing - original draft, Writing - review & editing, Resources.
Declaration of competing interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Acknowledgments
This project was supported by the National Natural Science Foundation of China (Grant No. 21427808), and the Fundamental Research Funds of Shandong University (2018JC017).
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