Triethoxysilane-derived silicon quantum dots: A novel pathway to small size and high crystallinity

Abstract

The crystalline fraction is a critical parameter for assessing the quality of silicon quantum dots (SiQDs), and its enhancement is anticipated to improve the optoelectronic performance of these materials. However, the crystalline fraction of small SiQDs produced through the pyrolysis of hydrogen silsesquioxane (HSQ) polymers still has significant potential for improvement. In this study, we successfully synthesized SiQDs with a diameter of approximately 3 nm and near-perfect crystallinity by optimizing the triethoxysilane (TES)/aqueous hydrochloric acid (HCl) volume ratio during the hydrolysis-condensation process of HSQ polymers. The SiQDs exhibited a photoluminescence (PL) center at 760 nm and an average PL quantum yield (PLQY) of 24.4%. Our findings demonstrate that the TES/aqueous HCl ratio significantly influences the proportion of cage structure and the cross-linking density of the network structure in HSQ polymers, which in turn governs SiQD size and crystallinity. A high proportion of cage structures in HSQ polymers promotes high crystallinity. Notably, an increased cross-linking density within the network structure results in elevated and uniform diffusion barriers. This phenomenon not only hinders the diffusion of silicon atoms, leading to smaller sizes but also facilitates the achievement of high crystallinity due to uniform diffusion. This work presents a novel approach to achieving exceptional crystalline in small SiQDs, with implications for advanced applications in lighting, display technologies, medical imaging, and photovoltaics.