Abstract
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.
Highlights
Electroluminescence from colloidal quantum dots (QDs), which was first reported in 1994, attracted lots of attentions from researchers working in the light-emitting diode (LED) fields
The results indicated that white EL emission from the Polymer light emitting diodes (PLEDs) originated from the hybridized graphene oxide quantum dots (GOQDs)-PVK complex emission with the contributions from individual GOQDs and PVK emissions
GOQDs were synthesized by modified hydrothermal deoxidization cutting of graphene oxide sheets (GOSs), which were prepared from natural graphite powder using a modified Hummers method[14]
Summary
Electroluminescence from colloidal quantum dots (QDs), which was first reported in 1994, attracted lots of attentions from researchers working in the light-emitting diode (LED) fields. Jeon’s group reported similar results using poly(9-vinylcarbazole (PVK) as host matrix[13] In both cases, it is suspected that EL from GQDs originated from (1) electron and hole transfer from the host to GQDs, which were injected into the host from the electron and hole transporting layers; (2) direct electron and hole injection into GQDs from the electron and hole transporting layers; and (3) energy transfer from the host to GQDs guest. We synthesized chemically functionalized fluorescent graphene oxide quantum dots (GOQDs) using a modified hydrothermal deoxidization method and fabricated simple structure of a PLED by blending GOQDs into a poly(N-vinyl carbazole) (PVK) polymer matrix. The results indicated that white EL emission from the PLED originated from the hybridized GOQDs-PVK complex emission with the contributions from individual GOQDs and PVK emissions
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