Easy extraction of water-soluble graphene quantum dots for light emitting diodes

Abstract

Graphene quantum dots (GQDs) have attracted a large amount of attention due to their unique optoelectronic properties, which arise from the quantum confinement effect or edge effect or surface functionalization. Popular routes for designing GQDs are based on the reactions in aqueous phases, which are detrimental for integration of GQDs into optoelectronic devices. Hence, a critical challenge remains in utilizing the water-soluble GQDs for fabricating optoelectronic devices. Here we demonstrate for the first time a single step facile route to extract water-soluble GQDs into solid powder under reduced pressure for the fabrication of light emitting diodes (LEDs). The process avoids the need for post synthesis ex situ functionalization or the use of additional polymers to make GQDs hydrophobic retaining the intrinsic luminescent behavior of GQDs. The measured current-voltage characteristics of GQD-LED devices showed a significantly low turn-on voltage of $2.5 V. Bias dependent electroluminescence leading to color tunability from blue to deep cyan is demonstrated.

Recent Advances in Graphene Quantum Dots: Synthesis, Properties, and Applications

“…GQDs can also be implemented in organic light‐emitting diodes (OLEDs) due to their high electron mobility and strong luminescence . Experiments conducted by Tang et al involved the coating of GQDs on an LED emitting at 410 nm to produce an additional, weaker emission peak at ≈510 nm, and thus generate cold‐white light through additive color mixing ( Figure ) …”

Recent advances in low‐dimensional semiconductor nanomaterials and their applications in high‐performance photodetectors

“…This gives QDs many advantages, including tunable bandgap, good light absorption, tunable photoluminescence (PL), high light stability, and good biocompatibility. It has a good application prospect in the fields of LEDs, PDs, and flexible electronics …”

“…It has a good application prospect in the fields of LEDs, PDs, and flexible electronics. [133][134][135][136] In addition, the formation of heterogeneous structures and devices between QDs and other 1D or 2D materials is also one of the research hotspots 125,[137][138][139] ; for example, graphene/Cu 2 O QDs PDs. 140 In order to make the device with higher responsive, Cu 2 O QDs are introduced on the basis of graphene.…”

Photochemical synthesis of doped graphene quantum dots and their photoluminescence in aqueous and solid states

“…5 Furthermore, most of the PL was detected from the colloid GQDs in past studies and fluorescence quenching may occur in the dry and aggregated state. 7,8 However, strong PL in solid stated GQDs is necessary for fabrication of advanced devices and other uses (e.g., inks and luminescence pattern printing). In addition, chemical doping is an effective way to tune the optical, chemical, and electronic properties of GQDs.…”

“…Due to the PL quenching resulting from the aggregation in the dried solid state photoluminescent nanoparticles, the applications of GQDs are significantly limited. 8,30 So far, there have been very few reports about PL from solid GQDs, especially GQDs not embedded in other matrix.8 To underline the potential applications of NGQDs prepared here in microoptoelectronic devices, printing inks and so on, emission properties were further investigated from NGQDs in the solid state. Colorful PL can be visualized clearly from the fluorescence images by excitation at different wavelengths.…”