Efficient Solid‐State Photoluminescence of Graphene Quantum Dots Embedded in Boron Oxynitride for AC‐Electroluminescent Device

Abstract

Emerging graphene quantum dots (GQDs) have received much attention for use as next-generation light-emitting diodes. However, in the solid-state, π-interaction-induced aggregation-caused photoluminescence (PL) quenching (ACQ) in GQDs makes it challenging to realize high-performance devices. Herein, GQDs incorporated with boron oxynitride (GQD@BNO) are prepared from a mixture of GQDs, boric acid, and urea in water via one-step microwave heating. Due to the effective dispersion in the BNO matrix, ACQ is significantly suppressed, resulting in high PL quantum yields (PL-QYs) of up to 36.4%, eightfold higher than that of pristine GQD in water. The PL-QY enhancement results from an increase in the spontaneous emission rate of GQDs due to the surrounding BNO matrix, which provides a high-refractive-index material and fluorescence energy transfer from the larger-gap BNO donor to the smaller-gap GQD acceptor. A high solid-state PL-QY makes the GQD@BNO an ideal active material for use in AC powder electroluminescent (ACPEL) devices, with the luminance of the first working GQD-based ACPEL device exceeding 283 cd m . This successful demonstration shows promise for the use of GQDs in the field of low-cost, ecofriendly electroluminescent devices.

Blue emission at atomically sharp 1D heterojunctions between graphene and h-BN

“…4b , the PL intensity of the 4L GQD/h-BN (red) was reduced compared to that of single-layer GQD/h-BN film (black). This indicates that the PL quenching still occurs in a structure that simply stacks GQD/h-BN films due to photon reabsorption and nonradiative energy transfer between GQDs in the vertical direction 33 , 34 . However, utilizing h-BN intercalation layers substantially improved the PL intensity since the charges generated on the GQD/h-BN film were not transported to GQDs in adjacent layers, blocked by the h-BN charge barrier (schematically shown in Fig.…”

Quenching‐Resistant Solid‐State Photoluminescence of Graphene Quantum Dots: Reduction of π−π Stacking by Surface Functionalization with POSS, PEG, and HDA

“…Due to such structural isolation of the luminophore, the GQDs have excellent photostability against water and oxygen. [8] In addition, the rigid sp 2 bonding network imparts high thermal stability to the luminescent GQDs, [9] as with part of the 2D graphene structure with high thermal conductivity. [10] While GQDs exhibit high optical stability against external stimuli, their highly aggregative nature through π−π stacking due to the van der Waals interaction between adjacent layers, [9,11] similar to polycyclic aromatic hydrocarbons (PAHs) or π−conjugated fluorescent polymers, greatly limits their application to optoelectronic devices as luminescent materials.…”

“…[8] In addition, the rigid sp 2 bonding network imparts high thermal stability to the luminescent GQDs, [9] as with part of the 2D graphene structure with high thermal conductivity. [10] While GQDs exhibit high optical stability against external stimuli, their highly aggregative nature through π−π stacking due to the van der Waals interaction between adjacent layers, [9,11] similar to polycyclic aromatic hydrocarbons (PAHs) or π−conjugated fluorescent polymers, greatly limits their application to optoelectronic devices as luminescent materials. The π−π stacking induces aggregationcaused PL quenching (ACQ) in the solid-state [12] and can cause problems such as an increase in uncontrolled electroluminescence (EL) due to intermolecular excimer formation, which especially debilitates the generation of pure emission color in light-emitting devices made thereof.…”

“…[13] Unfortunately, few efforts have been devoted to the prevention of ACQ, although it is one of the main obstacles to the application of GQDs to optoelectronic devices. Incorporation of GQDs into solid-state matrices such as boron oxynitride (BNO), [9] agar, [14] poly(vinyl alcohol) (PVA), [15] thermoplastic starch (TPS), [16] or a cellulose nanofiber-clay hybrid [17] is considered a partial solution to minimize ACQ by forming intermolecular interactions such as hydrogen bonding. However, this approach cannot fully resolve the ACQ when the GQD loading ratio exceeds 0.06 wt% in BNO, [9] 10.0 wt% in PVA, [15] or 10.9 wt% in TPS.…”

Eco‐Friendly, High‐Loading Luminescent Solar Concentrators with Concurrently Enhanced Optical Density and Quantum Yields While Without Sacrificing Edge‐Emission Efficiency

“…To prove the existence of hydrogen bonding within the composites, the XPS and FTIR measurements were performed and the experimental results are displayed in Figure . Figure (a) shows the XPS C1s spectra for both samples of GSH‐AuNCs and 26 wt.% GSH‐AuNCs/PVP composites.…”