Gram‐Scale Synthesis of Highly Efficient Rare‐Earth‐Element‐Free Red/Green/Blue Solid‐State Bandgap Fluorescent Carbon Quantum Rings for White Light‐Emitting Diodes

Abstract

The negative impact of rare-earth elements (REEs) on the environment, limited supply and high cost prompt the need for REE-free phosphor-converted white light-emitting diodes (LEDs). Here, we report the gram-scale synthesis of red/green/blue solid-state bandgap fluorescent carbon quantum rings (R/G/B-SBF-CQRs) with high quantum yields up to 30-46 %. This was achieved using cyano-group-bearing pphenyldiacetonitrile as precursor and forming carbon quantum rings of different diameters through the linkage of curved carbon quantum ribbons of different lengths. The results show the role of cyano groups in inducing the curvature of the carbon quantum ribbons for CQR formation and emission of stable solid-state bandgap fluorescence. R/G/B-SBF-CQRsphosphor-based LEDs emitted warm white light with low CCT (3576 K), high CRI (96.6), and high luminous efficiency (48.7 lm W À1 ), comparable to REE-phosphor-based LEDs.

Aggregation and luminescence in carbonized polymer dots

“…[33,34] These methods are instructive to realize solid emission in CPDs. [22,[35][36][37] Through chemically grafting polyhedral oligomeric silsesquioxane (POSS), poly(ethylene glycol) (PEG), and hexadecylamine (HDA) at the edge sites of bare CPDs by carbodiimide coupling, Jeon et al proposed surface functionalized CPDs to reduce ACQ (Figure 1C). [35] Introducing a large number of long alkyl chains on the surface, Shen et al prepared white-emitting CPDs via one-step carbonization of polyoxyethylene sorbitan monooleate (Figure 1D).…”

“…[35] Introducing a large number of long alkyl chains on the surface, Shen et al prepared white-emitting CPDs via one-step carbonization of polyoxyethylene sorbitan monooleate (Figure 1D). [37] Through elaborately designing precursors and synthesis processes, Zeng et al [22] and Fan et al [36] sequentially achieved the fabrication of carbon nanorings that can effectively avoid ACQ.…”

Carbon Dots in Bioimaging, Biosensing and Therapeutics: A Comprehensive Review

“…Interestingly, the as‐prepared CDs also exhibit size dependence, with the bandgap gradually decreasing with increasing size. [ 39 ]…”

Carbon dots: An innovative luminescent nanomaterial

“…For instance, the R/G/B-SBF-CQRs with high QYs up to 30-46% have been successfully applied to LEDs to achieve warm white light emission, which is promising to act as the substitute for traditional rare earth phosphors and realize industrialization in the future (Figure 7A). [137]…”