Polymer light emitting diodes (PLEDs) using quantum dots (QDs) as emissive materials have received much attention as promising components for next-generation displays. Despite their outstanding properties, toxic and hazardous nature of QDs is a serious impediment to their use in future eco-friendly opto-electronic device applications. Owing to the desires to develop new types of nano-material without health and environmental effects but with strong opto-electrical properties similar to QDs, graphene quantum dots (GQDs) have attracted great interest as promising luminophores. However, the origin of electroluminescence from GQDs incorporated PLEDs is unclear. Herein, we synthesized graphene oxide quantum dots (GOQDs) using a modified hydrothermal deoxidization method and characterized the PLED performance using GOQDs blended poly(N-vinyl carbazole) (PVK) as emissive layer. Simple device structure was used to reveal the origin of EL by excluding the contribution of and contamination from other layers. The energy transfer and interaction between the PVK host and GOQDs guest were investigated using steady-state PL, time-correlated single photon counting (TCSPC) and density functional theory (DFT) calculations. Experiments revealed that white EL emission from the PLED originated from the hybridized GOQD-PVK complex emission with the contributions from the individual GOQDs and PVK emissions.
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J. K. Kim and J. H. Park acknowledges the support by the NRF of Korea Grant funded by the Ministry of Science, ICT and Future Planning (NRF-2013R1A2A1A09014038, 2009-0083540, 2014M3A7B4052200). Dr. Chang-Lyoul Lee thanks for financial support by the Basic Science Research Program through Ministry of Education (NRF-2013R1A1A2006742) and the APRI research Program through a grant provided by the Gwangju Institute of Science and Technology. S. Bae appreciates the financial support from Korea Institute of Science and Technology (KIST) institutional program and the Graphene Materials/Components Development Project (10044366) through the Ministry of Trade, Industry, and Energy (MOTIE), Republic of Korea.
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