基于无机金属配体Ag-X（[AgS]-和[AgSe]-）修饰纳米晶的合成技术及其光电性能研究

The bottom-up chemical synthesis of various inorganic nanocrystals with well-designed size, shape, and composition has achieved great success over the past two decades. Because of their extraordinary physical and chemical properties, colloidal nanocrystals have many potential applications in light-emitting devices, photodetectors, solar cells, and other devices. However, the inherent long chain organic surface ligand capped on the nanocrystals resulted the poor interparticle electrical transport properties and make the practical applications doubtful. Very recently, molecular metal chalcogenide complexes (MCCs), such as [Sn2S6] and [Sn2Se6]4-, were found could serve as convenient inorganic ligands for colloidal nanocrystals. We have reported that inorganic Sn-X complex ([Sn2S6]4-，[Sn2Se6]4-) as MCC ligand could induce the formation of self-assembled Cu2S and Cu2-xSe nanoplates and their electrical transport properties were largely improved. The present project is proposed to design inorganic ligands to synthesize various colloidal nanocrystals. And such inorganic ligands are able to cross-link as-synthesized nanocrystals into ordered superstructures. This will address the electrical transport issues caused by traditional long chain organic ligans and make the inorganic ligand capped colloidal nanocrystals more potential in future optoelectric applications.

近年来，人们通过液相合成的方法得到了各种尺寸、形貌、组成可控的无机纳米晶。由于这些材料所表现出的新奇的物理和化学性质，使其在光电器件方面有着巨大的潜在应用价值。传统的纳米晶合成和组装大都利用有机配体作为表面修饰剂来保持其稳定性，由于这些有机配体导电性能差使得粒子之间的电荷传输能力较低，大大阻碍了其在光电器件中的应用。研究发现，无机硫属配合物作为纳米晶配体同样具有稳定纳米颗粒的作用，并且可以大大提高粒子间的电荷传输能力。最近，我们利用一种 Sn 的硫属无机配合物在有机相中直接合成了具有组装结构的 Cu2S和Cu2-xSe纳米晶，这种新的无机配体不仅改善了Cu2S和Cu2-xSe的电学性质，而且对其组装行为也有着重要影响。本项目将基于此开展新型无机金属配体修饰的纳米晶的合成技术研究，该技术有望改善量子点组装结构在光电器件应用中的界面电荷传输性能，从而有效提其在光电器件应用上的性能表现。

以“无膦法”合成了高质量的ZnxCd1-xSe/ZnS，ZnxCd1-xS/ZnS，CuInS2/ZnS，Cu2ZnSnS4 和Cu2ZnSnSe4等半导体量子点，其中ZnxCd1-xSe/ZnS，ZnxCd1-xS/ZnS，CuInS2/ZnS核壳结构量子点的最高量子产率分别可达85%，95%，72%，相应的荧光覆盖范围分别是460-550nm，400-460nm和560-750nm；进一步的，针对这些高质量的荧光量子点尝试了10g量级的规模化合成。对于自行合成得到的CuInS2（CIS）半导体等量子点，通过采用具有良好导电性能的(NH4)4Sn2S6作为无机配体对CIS半导体量子点表面原有有机配体的成功取代，得到具有无机配体修饰且电荷传输性能良好的CIS半导体量子点；配体交换后得到的CIS量子点电子耦合能力显著增强，旋涂成膜后的电荷传输性能也有较大幅度提高。同时，针对高量子产率的ZnxCd1-xSe/ZnS，ZnxCd1-xS/ZnS等量子点，通过采用结合力强的短链配体进行配体交换，既保证了荧光量子点的溶解性和量子产率，又大幅度提高了其成膜后载流子在量子点薄膜中的输运效率。基于这种短链配体的修饰技术，我们成功构筑了目前亮度最高的蓝光量子点发光器件（QD-LEDs），且蓝绿红三色QD-LEDs的外量子效率（EQE）均可达到10%以上。在非Cd体系QD-LEDs构筑方面，采用新近开发的“低温成核，高温包壳”技术合成了量子产率大于80%且稳定性良好的ZnSe/ZnS核壳结构量子点，并基于该量子点构筑了最大亮度可达2632 cd m-2，最大外量子效率可达7.83%的蓝紫色（428 nm）QD-LEDs，该亮度和效率较已有报道的最高值分别高出12倍和100倍。