Stability of Silicon Quantum Dots Against Solar Light/Hot Water: RGB Foldable Films and Ligand Engineering

Heavy-metal-free fluorophores such as silicon quantum dots (SiQDs) are required for next-generation light sources to address environmental concerns. However, few studies on SiQD devices are concerned with flexible devices, luminescence colors other than red, or stability data. Herein, the synthesis via three different methods of colloidal SiQDs exhibiting red/green/blue (RGB) photoluminescence (PL) is presented. The durability of each RGB SiQD embedded in a flexible polymer film (>4 x 4 cm2) and exposed to solar light or hot water is evaluated. The nature of the terminating ligand on the SiQD surface significantly affects PL stability. In particular, SiQDs passivated with siloxane groups exhibiting blue PL retained 80% of their initial PL intensity after solar -light exposure for 8 days. These blue SiQDs embedded in a film retain 94% of their original PL quantum yield (PLQY) after 12 days at 80 degrees C in water. The types of ligand, coverage, and host material properties (light absorptivity, permeability, and hydro-phobicity) are critical for enhancing the PLQY, radiative rate, and durability of SiQDs. These new insights are invaluable for designing heavy-metal-free light sources, accelerating their use, implementing them, and integrating them into curved substrates with soft textures and improved flexibility and stretchability, leading to foldable optoelectronics, e-skins, and wearable devices.

Automated summary

This study focuses on heavy-metal-free fluorophores, specifically silicon quantum dots (SiQDs), for next-generation light sources. The researchers synthesized SiQDs with red/green/blue photoluminescence (PL) using three different methods and evaluated their durability in flexible polymer films. They found that the nature of the terminating ligand on the SiQD surface significantly affected the PL stability. The insights gained from this study are important for designing light sources without heavy metals and integrating them into flexible and stretchable optoelectronic devices.