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Sensitizing crystalline silicon (c-Si) with an infrared-sensitive material, such as lead sulfide (PbS) colloidal quantum dots (CQDs), provides a straightforward strategy for enhancing the infrared-light sensitivity of a Si-based photodetector. However, it remains challenging to construct a high-efficiency photodetector based upon a Si:CQD heterojunction. Herein, we demonstrate that Si surface passivation is crucial for building a high-performance Si:CQD heterojunction photodetector. We have studied one-step methyl iodine (CH3I) and two-step chlorination/methylation processes for Si surface passivation. Transient photocurrent (TPC) and transient photovoltage (TPV) decay measurements reveal that the two-step passivated Si:CQD interface exhibits fewer trap states and decreased recombination rates. These passivated substrates were incorporated into prototype Si:CQD infrared photodiodes, and the best performance photodiode based upon the two-step passivation shows an external quantum efficiency (EQE) of 31% at 1280 nm, which represents a near 2-fold increase over the standard device based upon the one-step CH3I passivated Si.

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.

Silicon nanoparticles (SiNPs) can be challenging to prepare with defined size, crystallinity, composition, and surface chemistry. As is the case for any nanomaterial, controlling these parameters is essential if SiNPs are to realize their full potential in areas such as alternative energy generation and storage, sensors, and medical imaging. Numerous teams have explored and established innovative synthesis methods, as well as surface functionalization protocols to control these factors. Furthermore, substantial effort has been expended to understand how the abovementioned parameters influence material properties. In the present review we provide a commentary highlighting the benefits and limitations of available methods for preparing silicon nanoparticles as well as demonstrations of tailoring optical and electronic properties through definition of structure (i.e., crystalline vs. amorphous), composition and surface chemistry. Finally, we highlight potential opportunities for future SiNP studies.

Doped silicon nanocrystals (SiNCs) are promising materials that could find use in a wide variety of applications. Realizing methods to tailor the surface chemistry of these particles offers greater tunability of the material properties as well as broader solvent compatibility. Herein, we report organic-soluble B-doped SiNCs prepared via a thermal processing method followed by phosphorous pentachloride etching induced functionalization with alkoxy ligands of varied chain lengths. This approach provides a scalable route to solution processable B-doped SiNCs and establishes a potential avenue for the functionalization of other doped SiNCs.

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.

Doped silicon nanocrystals (SiNCs) are promising materials that could find use in a wide variety of applications. Realizing methods to tailor the surface chemistry of these particles offers greater tunability of the material properties as well as broader solvent compatibility. Herein, we report organic-soluble B-doped SiNCs prepared

Luminescent silicon nanoparticles have been widely recognized as an alternative for metal-based quantum dots (QDs) for optoelectronics partly because of the high abundance and biocompatibility of silicon. To date, the broad photoluminescence line width (often >100 nm) of silicon QDs has been a hurdle to achieving competitive spectral purity and incorporating them into light-emitting devices. Herein we report fabrication and testing of straightforward configuration of Fabry-Perot resonators that incorporates a thin layer of SiQD-polymer hybrid/blend between two reflective silver mirrors; remarkably these devices exhibit up-to-14-fold narrowing of SiQD emission and achieve a spectral bandwidth as narrow as ca. 9 nm. Our polymer-based, SiQD-containing Fabry-Perot resonators also provide convenient spectral tunability, can be prepared using a variety of polymer hosts and substrates, and enable rigid as well as flexible devices.

We introduce a straightforward and cost-effective water-assisted approach to transfer patterns of nanomaterials onto diverse substrates. The transfer method relies on the hydrophobic effect and utilizes a water-soluble polymer film as a carrier to transfer hydrophobic nanomaterials from a patterned source substrate onto a target substrate. Using this approach, nanomaterials are transferred readily from solutions onto surfaces of various shapes and compositions with high fidelity for feature sizes approaching 10 microns.

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.