Advances in Miniaturized Computational Spectrometers.

Miniaturized computational spectrometers have emerged as a promising strategy for miniaturized spectrometers, which breaks the compromise between footprint and performance in traditional miniaturized spectrometers by introducing computational resources. They have attracted widespread attention and a variety of materials, optical structures, and photodetectors are adopted to fabricate computational spectrometers with the cooperation of reconstruction algorithms. Here, a comprehensive review of miniaturized computational spectrometers, focusing on two crucial components: spectral encoding and reconstruction algorithms are provided.

Synergism in Binary Nanocrystals Enables Top-Illuminated HgTe Colloidal Quantum Dot Short-Wave Infrared Imager.

Thanks to their tunable infrared absorption, solution processability, and low fabrication costs, HgTe colloidal quantum dots (CQDs) are promising for optoelectronic devices. Despite advancements in device design, their potential for imaging applications remains underexplored. For integration with Si-based readout integrated circuits (ROICs), top illumination is necessary for simultaneous light absorption and signal acquisition.

In-Synthesis Se-Stabilization Enables Defect and Doping Engineering of HgTe Colloidal Quantum Dots.

Colloidal Quantum Dots (CQDs) of mercury telluride (HgTe) hold particular appeal for infrared photodetection due to their widely tunable infrared absorption and good compatibility with silicon electronics. While advances in surface chemistry have led to improved CQD solids, the chemical stability of HgTe material is not fully emphasized. In this study, it is aimed to address this issue and identifies a Se-stabilization strategy based on the surface coating of Se on HgTe CQDs via engineering in the precursor reactivity.

Short-Wave Infrared Detection and Imaging Employing Size-Customized HgTe Nanocrystals.

HgTe nanocrystals (NCs) possess advantages including tunable infrared absorption spectra, solution processability, and low fabrication costs, offering new avenues for the advancement of next-generation infrared detectors. In spite of great synthetic advances, it remains essential to achieve customized synthesis of HgTe NCs in terms of industrial applications. Herein, by taking advantage of a high critical nucleation concentration of HgTe NCs, a continuous-dropwise (CD) synthetic approach that features the addition of the anion precursors in a feasible drop-by-drop fashion is demonstrated.

Planar Cation Passivation on Colloidal Quantum Dots Enables High-Performance 0.35-1.8 µm Broadband TFT Imager.

Solution-processed colloidal quantum dots (CQDs) are promising candidates for broadband photodetectors from visible light to shortwave infrared (SWIR). However, large-size PbS CQDs sensitive to longer SWIR are mainly exposed with nonpolar (100) facets on the surface, which lack robust passivation strategies. Herein, an innovative passivation strategy that employs planar cation, is introduced to enable face-to-face coupling on (100) facets and strengthen halide passivation on (111) facets.

Colloidal PbS Quantum Dot Photodiode Imager with Suppressed Dark Current.

Lead sulfide (PbS) colloidal quantum dots (CQDs) for photodetectors (PDs) have garnered great attention due to their potential use as low-cost, high-performance, and large-area infrared focal plane arrays. The prevailing device architecture employed for PbS CQD PDs is the -- structure, where PbS CQD films treated with thiol molecules, such as 1,2-ethanedithiol (EDT), are widely used as -type layers due to their favorable band alignment. However, PbS-EDT films face a critical challenge associated with low film quality, resulting in many defects that curtail the device performance.

Flexible and broadband colloidal quantum dots photodiode array for pixel-level X-ray to near-infrared image fusion.

Combining information from multispectral images into a fused image is informative and beneficial for human or machine perception. Currently, multiple photodetectors with different response bands are used, which require complicated algorithms and systems to solve the pixel and position mismatch problem. An ideal solution would be pixel-level multispectral image fusion, which involves multispectral image using the same photodetector and circumventing the mismatch problem.

High-Performance and Stable Colloidal Quantum Dots Imager via Energy Band Engineering.

Solution-processed colloidal quantum dot (CQD) photodiodes are compatible for monolithic integration with silicon-based readout circuitry, enabling ultrahigh resolution and ultralow cost infrared imagers. However, top-illuminated CQD photodiodes for longer infrared imaging suffer from mismatched energy band alignment between narrow-bandgap CQDs and the electron transport layer. In this work, we designed a new top-illuminated structure by replacing the sputtered ZnO layer with a SnO layer by atomic layer deposition.

Large-area flexible colloidal-quantum-dot infrared photodiodes for photoplethysmogram signal measurements.

Epitaxially grown photodiodes are the foundation of infrared photodetection technology; however, their rigid structure and limited area scaling limit their use in advanced applications. Colloidal-quantum-dot (CQD) infrared photodiodes have increased active areas through solution processing, and are thus potential candidates for large-area flexible photodetection, but these large-area photodiodes have disadvantages such as large dark current density, poor homogeneity, and poor stability. Therefore, this study established a fabrication strategy for large-area flexible CQD photodiodes that involves introducing polyimide to CQD ink to improve CQD passivation, monodisperse ink persistence, and film morphology.

High-Performance Colloidal Quantum Dot Photodiodes via Suppressing Interface Defects.

PbS colloidal quantum dot (CQD) infrared photodiodes have attracted wide attention due to the prospect of developing cost-effective infrared imaging technology. Presently, ZnO films are widely used as the electron transport layer (ETL) of PbS CQDs infrared photodiodes. However, ZnO-based devices still suffer from the problems of large dark current and low repeatability, which are caused by the low crystallinity and sensitive surface of ZnO films.

Cation-Exchange Enables In Situ Preparation of PbSe Quantum Dot Ink for High Performance Solar Cells.

Lead selenide (PbSe) colloidal quantum dots (CQDs) are promising candidates for optoelectronic applications. To date, PbSe CQDs capped by halide ligands exhibit improved stability and solar cells using these CQDs as active layers have reported a remarkable power conversion efficiency (PCE) up to 10%. However, PbSe CQDs are more prone to oxidation, requiring delicate control over their processability and compromising their applications.

Ligand-Engineered HgTe Colloidal Quantum Dot Solids for Infrared Photodetectors.

HgTe colloidal quantum dots (CQDs) are promising absorber systems for infrared detection due to their widely tunable photoresponse in all infrared regions. Up to now, the best-performing HgTe CQD photodetectors have relied on using aggregated CQDs, limiting the device design, uniformity and performance. Herein, we report a ligand-engineered approach that produces well-separated HgTe CQDs.

Matching Charge Extraction Contact for Infrared PbS Colloidal Quantum Dot Solar Cells.

Infrared solar cells (IRSCs) can supplement silicon or perovskite SCs to broaden the utilization of the solar spectrum. As an ideal infrared photovoltaic material, PbS colloidal quantum dots (CQDs) with tunable bandgaps can make good use of solar energy, especially the infrared region. However, as the QD size increases, the energy level shrinking and surface facet evolution makes us reconsider the matching charge extraction contacts and the QD passivation strategy.

Phase-Transfer Exchange Lead Chalcogenide Colloidal Quantum Dots: Ink Preparation, Film Assembly, and Solar Cell Construction.

Solution-processed colloidal quantum dots (CQDs) are promising candidates for the third-generation photovoltaics due to their low cost and spectral tunability. The development of CQD solar cells mainly relies on high-quality CQD ink, smooth and dense film, and charge-extraction-favored device architectures. In particular, advances in the processing of CQDs are essential for high-quality QD solids.

Highly Luminescent Zero-Dimensional Organic Copper Halides for X-ray Scintillation.

The present work reports highly efficient flexible and reabsorption-free scintillators based on two zero-dimensional (0D) organic copper halides (TBA)CuX (TBA = tetrabutylammonium cation; X = Cl, Br). The (TBA)CuX exhibit highly luminescent green and sky-blue emissions peaked at 510 and 498 nm, with large Stokes shifts of 224 and 209 nm and high photoluminescence quantum yields (PLQYs) of 92.8% and 80.

Efficient Dual-Band White-Light Emission with High Color Rendering from Zero-Dimensional Organic Copper Iodide.

Broad-band white-light emissions from organic-inorganic lead halide hybrids have attracted considerable attention in energy-saving solid-state lighting (SSL) applications. However, the toxicity of lead in these hybrids hinders their commercial prospects, and the low photoluminescence quantum yields (PLQYs) cannot meet the requirements for efficient lighting. Here, we report a highly efficient dual-band white-light emission from organic copper iodide, (CHN)CuI, which exhibits a high PLQY of 54.

Efficiently Passivated PbSe Quantum Dot Solids for Infrared Photovoltaics.

Infrared (IR) solar cells are promising devices for significantly improving the power conversion efficiency of common solar cells by harvesting the low-energy IR photons. PbSe quantum dots (QDs) are superior IR photon absorbing materials due to their strong quantum confinement and thus strong interdot electronic coupling. However, the high chemical activity of PbSe QDs leads to etching and poor passivation in ligand exchange, resulting in a high trap-state density and a high open circuit voltage () deficit.

Direct Optical Patterning of Quantum Dot Light-Emitting Diodes via In Situ Ligand Exchange.

Precise patterning of quantum dot (QD) layers is an important prerequisite for fabricating QD light-emitting diode (QLED) displays and other optoelectronic devices. However, conventional patterning methods cannot simultaneously meet the stringent requirements of resolution, throughput, and uniformity of the pattern profile while maintaining a high photoluminescence quantum yield (PLQY) of the patterned QD layers. Here, a specially designed nanocrystal ink is introduced, "photopatternable emissive nanocrystals" (PENs), which satisfies these requirements.

Efficient and Reabsorption-Free Radioluminescence in CsCuI Nanocrystals with Self-Trapped Excitons.

Radioluminescent materials (scintillators) are widely applied in medical imaging, nondestructive testing, security inspection, nuclear and radiation industries, and scientific research. Recently, all-inorganic lead halide perovskite nanocrystal (NC) scintillators have attracted great attention due to their facile solution processability and ultrasensitive X-ray detection, which allows for large area and flexible X-ray imaging. However, the light yield of these perovskite NCs is relatively low because of the strong self-absorption that reduces the light out-coupling efficiency.

Quantum dot solids showing state-resolved band-like transport.

Improving charge mobility in quantum dot (QD) films is important for the performance of photodetectors, solar cells and light-emitting diodes. However, these applications also require preservation of well defined QD electronic states and optical transitions. Here, we present HgTe QD films that show high mobility for charges transported through discrete QD states.

Conduction Band Fine Structure in Colloidal HgTe Quantum Dots.

HgTe colloidal quantum dots (QDs) are of interest because quantum confinement of semimetallic bulk HgTe allows one to synthetically control the bandgap throughout the infrared. Here, we synthesize highly monodisperse HgTe QDs and tune their doping both chemically and electrochemically. The monodispersity of the QDs was evaluated using small-angle X-ray scattering (SAXS) and suggests a diameter distribution of ∼10% across multiple batches of different sizes.

Mixed-quantum-dot solar cells.

Colloidal quantum dots are emerging solution-processed materials for large-scale and low-cost photovoltaics. The recent advent of quantum dot inks has overcome the prior need for solid-state exchanges that previously added cost, complexity, and morphological disruption to the quantum dot solid. Unfortunately, these inks remain limited by the photocarrier diffusion length.

Hybrid Colloidal Stabilization Mechanism toward Improved Photoluminescence and Stability of CdSe/CdS Core/Shell Quantum Dots.

Colloidal quantum dots can be stabilized in either a polar solvent or a nonpolar solvent depending on their surface chemistry. The former is typically achieved by charge stabilization while the latter by steric hindrance. This allows reversible tuning of their surface polarity for targeted application by engineering their ligand profile.

Efficient and stable solution-processed planar perovskite solar cells via contact passivation.

Planar perovskite solar cells (PSCs) made entirely via solution processing at low temperatures (<150°C) offer promise for simple manufacturing, compatibility with flexible substrates, and perovskite-based tandem devices. However, these PSCs require an electron-selective layer that performs well with similar processing. We report a contact-passivation strategy using chlorine-capped TiO colloidal nanocrystal film that mitigates interfacial recombination and improves interface binding in low-temperature planar solar cells.

Hybrid organic-inorganic inks flatten the energy landscape in colloidal quantum dot solids.

Bandtail states in disordered semiconductor materials result in losses in open-circuit voltage (V) and inhibit carrier transport in photovoltaics. For colloidal quantum dot (CQD) films that promise low-cost, large-area, air-stable photovoltaics, bandtails are determined by CQD synthetic polydispersity and inhomogeneous aggregation during the ligand-exchange process. Here we introduce a new method for the synthesis of solution-phase ligand-exchanged CQD inks that enable a flat energy landscape and an advantageously high packing density.