Ultra‐Narrow‐Bandwidth Deep‐Red Electroluminescence Based on Green Plant‐Derived Carbon Dots

Abstract

Deep‐red light‐emitting diodes (DR‐LEDs, >660 nm) with high color‐purity and narrow‐bandwidth emission are promising for full‐color displays and solid‐state lighting applications. Currently, the DR‐LEDs are mainly based on conventional emitters such as organic materials and heavy‐metal based quantum dots (QDs) and perovskites. However, the organic materials always suffer from the complicated synthesis, inferior color purity with full‐width at half‐maximum (FWHM) more than 40 nm, and the QDs and perovskites still suffer from serious problems related to toxicity. Herein, this work reports the synthesis of efficient and high color‐purity deep‐red carbon dots (CDs) with a record narrow FWHM of 21 nm and a high quantum yield of more than 50% from readily available green plants. Moreover, an exciplex host is further established using a polymer and small molecular blend, which has been shown to be an efficient strategy for producing high color‐purity monochrome emission from deep‐red CDs via Förster energy transfer (FET). The deep‐red CD‐LEDs display high color‐purity with Commission Internationale de l'Eclairage (CIE) coordinates of (0.692, 0.307). To the best of the knowledge, this is the first report of high color‐purity CD‐LEDs in the deep‐red region, opening the door for the application of CDs in the development of high‐resolution light‐emitting display technologies.

Confinement-Modulated Clusterization-Triggered Time-Dependent Phosphorescence Color from Xylan-Carbonized Polymer Dots

“…Xylan with good RTP performance is chosen to prepare CPDs because it is a paper-mill or viscose fiber-mill byproduct that is normally cast aside, which is highly low-cost and eco-friendly. More importantly, unlike other biomass (such as cucumber skin, fruits, rice husks, and green plant) used to synthesize CDs, xylan composed of β-(1 → 4)-linked backbones of xylose possesses a well-defined structure, conductive to theoretically elucidate the relationship between structure and PL performance (will discuss below). Carboxyl groups are grafted on xylan chains by carboxymethylation to afford water-soluble carboxymethyl xylan (CMX) (Figures S2 and S3).…”

Optimizing charge balance in carbon dot-based LEDs for enhanced performance

“…It has been reported that the voids in ZnMgO films can be effectively filled with PVP molecules to form dense films to efficiently reduce the leakage current. 59 Therefore, for the fabricated devices, insulating polymer PVP was introduced into the ETL based on ZnMgO nanoparticles to modulate the electron mobility. The EL spectra of CDs-LEDs with different ratios of ZnMgO and PVP are compared in Fig.…”

“…S15 (ESI†) that no new light energy groups appear, that is, no chemical reaction occurs to produce new substances, thus the EL spectrum of the device is a composite spectrum. 58,59 When the doping ratio of CBP&CDs is 1 : 8, the fabricated CDs-LED with CIE coordinates of (0.30, 0.47) is obtained (Fig. 4(b)), corresponding to green light emission.…”

Fluorescent carbon dots from birch leaves for sustainable electroluminescent devices

“…47,48 However, it is notable that this issue was recently successfully addressed by Chen and co-workers when they synthesized clover-derived bio-CDs, which delivered emission with a narrow FWHM of 25 nm in an OLED device. 49…”