Record-Breaking Far-Red Silicon Quantum Dots LEDs Enabled by Solvent Engineering: Toward Superseding Perovskite Quantum Dots.

Abstract

Most quantum dots (QDs) contain either toxic elements, which are health and environmental hazards, or costly precious metals. In contrast, as nanocrystals consisting mainly of an earth-abundant, light element, silicon QDs (SiQDs) have attracted attention as cost-effective biomedical, display, and solid-state lighting materials. However, unlike heavy-metal or perovskite QDs, SiQDs have not yet been used to create high-performance optoelectronics or long-lifetime light-emitting diodes (LEDs). Herein, the fabrication via solvent engineering of SiQD LEDs with record-breaking external quantum efficiency (16.5%) and lifetimes up to 733 times longer than the previous record is reported. Furthermore, the far-red (750 nm) luminance is comparable to that of state-of-the-art perovskite QD LEDs. Dispersing the SiQDs in octane yields particularly efficient LEDs owing to negligible SiQD aggregation, and Joule heating minimization realizes long-term stability (lifetime >200 h). Thus, solvent engineering is harnessed to break four QD LED performance records-for efficiency, luminance, voltage, and operational lifetime-using a more sustainable QD material, and the mechanisms underlying these performance improvements are unveiled. Thus, a new solvent-engineering approach for developing efficient, stable, and sustainable far-red SiQD LEDs, which are valuable light sources for applications including plant growth acceleration and photodynamic therapy, is highlighted.