Enhanced Emission of Nanocrystal Solids Featuring Slowly Diffusive Excitons

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• 作者：Natalia Kholmicheva ; Natalia Razgoniaeva ; Priyanka Yadav ; Adam Lahey ; Christian Erickson ; Pavel Moroz ; Daniel GamelinMikhail Zamkov
• 刊名：Journal of Physical Chemistry C
• 出版年：2017
• 出版时间：January 26, 2017
• 年：2017
• 卷：121
• 期：3
• 页码：1477-1487
• 全文大小：675K
• ISSN：1932-7455

文摘

Solution processing of semiconductor nanocrystal (NC) solids represents an attractive platform for the development of next-generation optoelectronic devices. In search of enhanced light-emitting performance, NC solids are typically designed to have large interparticle gaps that minimize exciton diffusion to dissociative sites. This strategy, however, reduces electrical coupling between nanoparticles in a film, making the injection of charges inefficient. Here, we demonstrate that bright emission from nanocrystal solids can be achieved without compromising their electrical conductivity. Our study shows that solids featuring a low absorption-emission spectral overlap (J) exhibit an intrinsically slower exciton diffusion to recombination centers, promoting longer exciton lifetimes. As a result, enhanced emission is achieved despite a strong electronic coupling. The observed phenomenon was found consistent with a decreased resonant energy transfer in films exhibiting a reduced J value. The inverse correlation between film luminescence and J was revealed through a comparative analysis of CdSe/CdS and ZnSe/CdS solids and further confirmed in two control systems (ZnTe/CdSe and Mn²⁺-doped ZnCdSe/ZnS). Exceptionally slow exciton diffusion (∼0.3 ms) and high brightness were observed for Mn²⁺-doped Zn_1–xCd_xSe/ZnS NC films exhibiting a nearly vanishing J parameter. We expect that the demonstrated combination of electrical coupling and bright emission in nanocrystal solids featuring low J can benefit the development of nanocrystal light-emitting technologies.