Silicon nanoparticles 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...

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 (CH 3 I) 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 CH 3 I passivated Si.

the alternatives, [7] Si is attractive because of its abundance, biocompatibility, [8] compatibility with silicon-based electronics, [9] luminescent properties when formed as QDs and established/tailorable surface chemistry. [10] EL of silicon-based nanomaterials (e.g., porous silicon, [11] Si nanocrystals in solid matrices [12] ) was first reported in the early 1990s and 2000s with low external quantum efficiencies (EQE) from 10 −6 to 1%. Of late, attention has shifted to colloidal silicon quantum dots (SiQDs) as potential active materials in hybrid organic light-emitting diodes (OLED) structures because of their promising EQE of up to 8.6% for near infrared (NIR) EL and 6.2% for red EL. [9a] Even with these improved metrics, the practical potential SiQD-LEDs remains limited by broad EL bandwidths with full-width-at-half-max-

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...

Integrating lead sulfide (PbS) colloidal quantum dots (CQDs) with crystalline silicon (c-Si) has been proven to be an effective strategy in extending the sensitivity of Si-based photodetectors into infrared regime. Here, we demonstrate the successful integration of PbS CQD inks with Si and construct a highly efficient heterojunction infrared photodiode operating in the range from 800 up to 1500 nm. Thanks to the well-passivated Si surface by a two-step chlorination/methylation method and high-quality CQD inks, the heterojunction photodiode yields a low density of trap states, as validated by transient photovoltage and photocurrent measurements. With an insertion layer of a p-type CQD capped with 1,2-ethanedithiol ligands, the built-in electric field is much enhanced, leading to improved charge extractions. As a result, we have obtained an external quantum efficiency (EQE) of 44% at the excitonic wavelength of 1280 nm. The EQE values are maintained without detectable degradation through the course of more than 600 h, achieving superior device stability. In contrast to commercial solutions, which require high-temperature epitaxial deposition of germanium (Ge) or III−V compounds, the presented single-step spin-coating process of CQD inks also enables large-area integration on Si.

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 lightemitting devices. Herein we report fabrication and testing of straightforward configuration of Fabry−Peŕot 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− Peŕot 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.

The discovery of metallic conductivity in polyacetylene [‐HC=CH‐]n upon doping represents a landmark achievement. However, the insolubility of polyacetylene and a dearth of methods for its chemical modification have limited its widespread use. Here, we employ a ring‐opening metathesis polymerization (ROMP) protocol to prepare functionalized polyacetylenes (fPAs) bearing: (1) electron‐deficient boryl (‐BR2) and phosphoryl (‐P(O)R2) side chains; (2) electron‐donating amino (‐NR2) groups, and (3) ring‐fused 1,2,3‐triazolium units via strain‐promoted Click chemistry. These functional groups render most of the fPAs soluble and can lead to intense light absorption across the visible to near‐IR region. Also, the presence of redox‐active boryl and amino groups leads to opposing near‐IR optical responses upon (electro)chemical reduction or oxidation. Some of the resulting fPAs show greatly enhanced air stability when compared to known polyacetylenes. Lastly, these fPAs can be cross‐linked to yield network materials with the full retention of optical properties.

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.