Highly efficient fabrication of lemon peel-derived carbon quantum dots for multicolor light-emitting diodes†

Biomass-derived carbon quantum dots (CQDs) have emerged as a promising sustainable alternative to conventional semiconductor quantum dots for light-emitting diode (LED) applications, offering distinct advantages in terms of renewability, low toxicity, and environmental friendliness. However, the efficient preparation of multicolor biomass-derived CQDs remains a critical challenge for practical implementation. In this study, lemon peel was screened as the optimal precursor from 26 types of agricultural and forestry residues, landscaping wastes, and food wastes. A green synthesis strategy involving hydrothermal carbonization coupled with controlled heteroatom doping was developed, which enabled the preparation of multicolor CQDs with superior photoluminescence properties. The synthesized CQDs exhibited tunable emission wavelengths (440–655 nm), high fluorescence quantum yields (4.98–35.58%), and exceptional photostability. High-efficiency LEDs were successfully fabricated by constructing a multilayer device structure using a mixture of multicolor biomass-derived CQDs and polymers. The CQD-based LEDs exhibited high color rendering indices (81.8–92.9) and a wide color temperature range (3912–6964 K) covering the visible spectrum while maintaining a decay rate below 30% over an operating lifetime of 11 832–12 815 h. This work not only provides a novel route for low-cost and sustainable synthesis of CQDs but also establishes theoretical and technical foundations for green electronic devices, accelerating the application of biomass resources in high-value optoelectronic devices.