Abstract
Solution-processed, non-toxic carbon dots (CDs) have attracted much attention due to their unique photoluminescence (PL) properties. They are promising emissive layers for flexible light-emitting devices. To this end, the CDs in pristine aqueous solutions need to be transferred to form solid-state thin films without sacrificing their original PL characteristics. Unfortunately, solid-state PL quenching induced by extra non-radiative (NR) energy transfer among CDs would significantly hinder their practical applications in optoelectronics. Here, a facile, low-cost and effective method has been utilized to fabricate high-performance CD/polymer light-emitting flexible films with submicron-structured patterns. The patterned polymers can serve as a solid matrix to disperse and passivate CDs, thus achieving high internal quantum yields of 61%. In addition, they can act as an out-coupler to mitigate the waveguide-mode losses, approximately doubling the external light-extraction efficiency. Such CD/polymer composites also exhibit good photo-stability, and thus can be used as eco-friendly, low-cost phosphors for solid-state lighting.
Highlights
In addition to the benefits inherited from carbon-based nano-materials, such as the low-cost and abundant raw materials, simple synthesis and solution-processed manufacturing properties, the carbon dots (CDs) exhibit some unique photo-physical properties, including tunable PL properties spanning the whole visible spectrum[5] and excellent photo-stability when dispersed in an aqueous solution.[6]
This work prepared flexible light-emitting thin films, consisting of CDs and Poly(vinyl alcohol) (PVA) polymers, which can exhibit enhanced PL properties to further extend the utility of CDs in solution, in particular, to serve as down-conversion phosphors for flexible light-emitting devices
The quantum yields (QYs) of the PL emission for CDs in aqueous solution are ~0.17, which are obtained by an absolute-QY measurement based on an integrating sphere combined with a spectrometer and a photo-detector
Summary
In addition to the benefits inherited from carbon-based nano-materials, such as the low-cost and abundant raw materials, simple synthesis and solution-processed manufacturing properties, the CDs exhibit some unique photo-physical properties, including tunable PL properties spanning the whole visible spectrum[5] and excellent photo-stability when dispersed in an aqueous solution.[6]. It is essential to develop high-performance solid-state light-emitting thin films that can retain their original PL emission properties while mitigating the waveguide-mode losses, so they can serve as efficient phosphors for prospective applications in flexible light-emitting devices.
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