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Luminescent colloidal silicon quantum dots (SiQDs) have been explored as alternatives to metal-based QDs for light-emitting diodes (LEDs) because of the abundance and biocompatibility of silicon. To date, the broad electroluminescence (EL) bandwidth (> 100 nm) and blue-shifting of EL at high applied voltages of SiQD-LEDs have been outstanding challenges that limited competitive spectral purity and device stability. Herein, we report the fabrication and testing of SiQD-LEDs that incorporate a Fabry-Pérot cavity that exhibit a narrow spectral linewidth as low as ca. 23 nm. The presented devices also provide spectral and visual stability from +4 V to +8 V, as well as spectral tunability.

Doped silicon quantum dots (SiQDs) with defined dopant distribution, size, and surface chemistry are highly sought-after as a scientific curiosity because their unique properties offer a wide array of potential applications including multi-modal medical imaging and photovoltaic devices. This report describes a diffusion based post-synthesis doping method for incorporating high concentrations of B (2.5 – 5.0 atomic %) into pre-formed SiQDs of predefined sizes while simultaneously maintaining their structure and morphology. The processing temperature, atmosphere, and QD size all strongly influence the resulting B-doped SiQDs. The as-synthesized doped SiQDs exhibit size-dependent photoluminescence spanning the visible to near-infrared spectral regions, are compatible with aqueous environments and are readily rendered compatible with organic solvents upon functionalization with appropriate alkoxide surface groups.

Current LED lights are created with quantum dots made of metals like selenium, tellurium, and cadmium which can be toxic. Silicon is used as a non-toxic substance and is the second most abundant element in the earth's crust. When silicon is prepared at a nanometer size, unique luminesce optical properties emerge that can be tuned using sized surface chemistry. Therefore, silicon nanoparticles can be used as an alternative emitter for LED lights. To produce hydride-terminated silicon nanoparticles we must synthesize the particles. Hydrogen silsesquioxane (HSQ) is processed at 1100 °C for one hour causing Si to cluster and form a SiO2 matrix, also known as the composite. The composite is then manually crushed in ethanol. The solution is further ground using glass beads, then filtered to get the composite powder. The final step is the HF etching. The hydride-terminated particles are then functionalized using three different methods to synthesize silicon nanoparticle-polystyrene hybrids, which determine the magnitude of luminosity and the quality of the hybrids. We spin coat each method and results were analyzed. Method 1 uses heat to functionalize hydride-terminated silicon nanoparticles with styrene. This process also causes styrene to attach to styrene to form a polystyrene chain. Method 1 gave a homogeneous mixture which yielded a consistent, bright and homogenous film. In method 2, dodecyl-terminated silicon nanoparticles are mixed with premade polystyrene. While this method gave better control of the amount of silicon nanoparticles inside the polymer hybrid, a homogeneous mixture was not created due to the different structures of polystyrene and dodecyl chains. Method 3 has dodecyl-terminated silicon with in-situ styrene polymerization. It generated a homogeneous mixture. The in-situ polymerization stabilizes the particles, allowing for brighter luminescence. Because of the stability and lower molecular weight, the mixture was easier to dissolve. We concluded that the different methods resulted in different polymer molecular weights and this created distinct properties between the polymer hybrids when spin-coating.