Article pubs.acs.org/cm
Hybrid ZnO-Based Nanoconjugate for Efficient and Sustainable White Light Generation Arunasish Layek, Paul C. Stanish, Vadim Chirmanov, and Pavle V. Radovanovic* Department of Chemistry, University of Waterloo, 200 University Avenue West, Waterloo, ON N2L 3G1, Canada S Supporting Information *
ABSTRACT: Developing new ways of generating white light is of paramount importance for the design of the next generation of smart, energy-efficient lighting sources. Here we report tunable white light emission of hybrid organic− inorganic nanostructures based on colloidal ZnO nanocrystals conjugated with organic fluorophores. These materials act as single nanophosphors owing to the distance-dependent energy transfer between the two components. The defect-based sizetunable ZnO nanocrystal blue-green emission coupled with complementary color emission from different fluorophores allows for the generation of white light with targeted chromaticity, color temperature, and color rendering index. We further show that silane layer-protected nanoconjugates result in increased stability of white light emission over a long period of time. The results of this work demonstrate an inexpensive, green, and sustainable approach to general solid-state lighting, without the use of rare earth or heavy metals. Colloidal form of the reported hybrid nanoconjugates allows for their further functionalization or incorporation into light-emitting devices. More broadly, size dependence of the electronic structure of native defects in transparent metal oxide nanocrystals and their electronic coupling with conjugated organic species could also represent a vehicle for introducing and manipulating new properties in these hybrid nanostructures.
■
(Ce 3+:YAG).10,14−16 These GaN/Ce3+:YAG and similar phosphor-converted WLEDs generally suffer from the deficiency of the red emission component, resulting in low color rendering index (CRI < 80%) and high correlated color temperature (CCT ≈ 7000 K).16,17 The past decade has seen an ongoing effort to develop rare earth element-based converters that could produce optimal quality white light in conjunction with blue LEDs.18−20 However, increasing deficiency and strategic importance of rare earth elements call for investigating other approaches to WLEDs.21,22 The slow adoption of WLED technologies is exacerbated by complex design and inconsistency of key figures of merit, ultimately leading to a high device manufacturing cost. In order to fully realize the potential of solid state lighting, new materials and technologies must be developed to generate desired quality of white light in an energy-efficient and economically viable way. Although organic semiconductor light emitting diodes (OLEDs) have been used to fabricate low-cost large-area white light illuminating panels, these devices are typically still plagued with short lifespan, low efficiency, and instability problems.23−25 An attractive alternative is to use highly luminescent colloidal semiconductor nanocrystals (NCs), which combine higher resistance to thermal and photo-
INTRODUCTION The ever increasing energy demands along with alarming concerns over global warming and climate change place an enormous importance on the investigation of new highefficiency lighting sources to reduce the world’s electricity usage.1−4 Because of the poor energy conversion efficiency of incandescent light bulbs (
