Sensitive and Low-Noise Perovskite Nanocrystal-Organic Bulk Heterostructure X-ray Detectors Enabled by Sodium Bromide-Assisted In Situ Reparation.

Perovskite nanocrystals (PNCs) offer unique advantages in large-area and thick-film deposition for X-ray detection applications due to the decoupling of the crystallization of perovskite from film formation, as well as their low-temperature and scalable deposition methods. However, the partial detachment of long-chain ligands in PNCs during the purification process would lead to the exposure of surface defects, making it challenging to ensure efficient charge carrier extraction and stable X-ray detection. In this study, we propose a beneficial strategy that involves the in situ reparation of these exposed defects with sodium bromide (NaBr) during the purification process to construct CsPbBr3 PNC-organic bulk heterostructure X-ray detectors. The NaBr-passivated PNCs exhibit stronger photoluminescence intensity and lower trap density in films compared to those of the control samples, confirming the effective passivation of halide vacancy defects. Furthermore, the NiOx hole transport layer with remarkable electron blocking capability is introduced to further suppress the dark current of the devices. Consequently, the optimal devices exhibit a large sensitivity of 4237 µC Gyair-1 cm-2 and a low dark current density of 10 nA cm-2, as well as improved operational stability, which allows for high-contrast and low-dose X-ray imaging applications.

All-silicon multidimensionally-encoded optical physical unclonable functions for integrated circuit anti-counterfeiting.

Integrated circuit anti-counterfeiting based on optical physical unclonable functions (PUFs) plays a crucial role in guaranteeing secure identification and authentication for Internet of Things (IoT) devices. While considerable efforts have been devoted to exploring optical PUFs, two critical challenges remain: incompatibility with the complementary metal-oxide-semiconductor (CMOS) technology and limited information entropy. Here, we demonstrate all-silicon multidimensionally-encoded optical PUFs fabricated by integrating silicon (Si) metasurface and erbium-doped Si quantum dots (Er-Si QDs) with a CMOS-compatible procedure. Five in-situ optical responses have been manifested within a single pixel, rendering an ultrahigh information entropy of 2.32 bits/pixel. The position-dependent optical responses originate from the position-dependent radiation field and Purcell effect. Our evaluation highlights their potential in IoT security through advanced metrics like bit uniformity, similarity, intra- and inter-Hamming distance, false-acceptance and rejection rates, and encoding capacity. We finally demonstrate the implementation of efficient lightweight mutual authentication protocols for IoT applications by using the all-Si multidimensionally-encoded optical PUFs.

HCOO- Doping-Induced Multiexciton Emissions in Cs3Cu2I5 Crystals for Efficient X-Ray Scintillation.

Self-trapped exciton (STE) luminescence, typically associated with structural deformation of excited states, has attracted significant attention in metal halide materials recently. However, the mechanism of multiexciton STE emissions in certain metal halide crystals remains largely unexplored. This study investigates dual luminescence emissions in HCOO- doped Cs3Cu2I5 single crystals using transient and steady-state spectroscopy. The dual emissions are attributed to intrinsic STE luminescence originating from the host lattice and extrinsic STE luminescence induced by external dopants, respectively, each of which can be triggered independently at distinct energy levels. Theoretical calculations reveal that multiexciton emission originates from structural distortion of the host and dopant STEs within the 0D lattice in their respective excited states. By meticulously tuning the excitation wavelength and selectively exciting different STEs, the dynamic alteration of color change in Cs3Cu2I5:HCOO- crystals is demonstrated. Ultimately, owing to an extraordinarily high photoluminescence quantum yield (99.01%) and a diminished degree of self-absorption in Cs3Cu2I5:HCOO- crystals, they exhibit remarkable X-ray scintillation characteristics with light yield being improved by 5.4 times as compared to that of pristine Cs3Cu2I5 crystals, opening up exciting avenues for achieving low-dose X-ray detection and imaging.

Monolithic integration of perovskite heterojunction on TFT backplanes through vapor deposition for sensitive and stable x-ray imaging.

Metal halide perovskites exhibit substantial potential for advancing next-generation x-ray detection. However, fabricating high-performance pixelated imaging arrays remains challenging due to the substantial dark current density and stability issues associated with common organic-inorganic hybrid perovskites. Here, we develop a vapor deposition method to create the first all-inorganic perovskite heterojunction film. The heterojunction introduction effectively reduces the dark current density of detectors to about 0.8 nA·cm-2, satisfying thin-film transistor (TFT) integration standards, while also increases sensitivity to above 2.6 × 104 µC·Gyair-1·cm-2, thus giving rise to a record low detection limit of <1 nGyair·s-1 among all polycrystalline perovskite-based x-ray detectors. The devices also demonstrate remarkable stability across multifarious demanding working conditions. Last, through monolithic integration of the heterojunction film with a 64 × 64 pixelated TFT array, we have achieved high-resolution real-time x-ray imaging, which paves the way for the application of all-inorganic perovskite in low-dose flat-panel x-ray detection.

Strain regulates the photovoltaic performance of thick-film perovskites.

Perovskite photovoltaics, typically based on a solution-processed perovskite layer with a film thickness of a few hundred nanometres, have emerged as a leading thin-film photovoltaic technology. Nevertheless, many critical issues pose challenges to its commercialization progress, including industrial compatibility, stability, scalability and reliability. A thicker perovskite film on a scale of micrometres could mitigate these issues. However, the efficiencies of thick-film perovskite cells lag behind those with nanometre film thickness. With the mechanism remaining elusive, the community has long been under the impression that the limiting factor lies in the short carrier lifetime as a result of defects. Here, by constructing a perovskite system with extraordinarily long carrier lifetime, we rule out the restrictions of carrier lifetime on the device performance. Through this, we unveil the critical role of the ignored lattice strain in thick films. Our results provide insights into the factors limiting the performance of thick-film perovskite devices.

Suppression of Randomness in Electrically Pumped Random Lasing from a ZnO Film-Based Light-Emitting Device on Silicon.

We report on the suppressed randomness in electrically pumped random lasing (RL) from a light-emitting device (LED) based on a metal-insulator-semiconductor (MIS) structure of Au/SiOx (x < 2)/ZnO on a silicon substrate, by means of patterning the light-emitting ZnO polycrystalline film into a number of square blocks separated by streets that are filled with the SiOx insulator. It is found that the RL modes can be remarkably reduced by shrinking the blocks in the absence of interblock optical coupling. Meanwhile, with the imposition of interblock optical coupling by shrinking the streets, the RL modes can be further reduced, and more importantly, the strongest mode wavelength is stabilized around 380 nm, where the ZnO film exhibits the largest optical gain.

A universal synthesis strategy of Pd-based trimetallic nanowires for efficient alcohol electrooxidation.

Trimetallic nanowires (NWs) have drawn much attention in efficient alcohol oxidation reaction (AOR) due to their unique features, including high atomic utilization efficiency and fast electron transfer ability. However, a universal strategy to synthesize Pd-based trimetallic NWs with high catalytic performance is still lacking. Herein, we develop a universal method for facile synthesis of PdBiM (M = Pt, Ru, Ir, Co, Cu) NWs with excellent AOR activities. By taking PdBiPt NWs as an example, the formation mechanism was investigated, and it is found that introduction of bismuth (Bi) plays an important role in facilitating the formation of the NW structure. Moreover, the PdBiPt NWs deliver an outstanding performance toward both the ethanol oxidation reaction (EOR) and the methanol oxidation reaction (MOR). Density functional theory (DFT) calculations together with experimental results disclose that the moderate electronic structure of trimetallic PdBiPt NWs can optimize the adsorption of OHads and weaken the adsorption of COads, thereby leading to the substantially enhanced AOR performance. We believe that this work can inspire the design of multimetallic NWs as high-performance catalysts.

Direct growth of graphene on hyper-doped silicon to enhance carrier transport for infrared photodetection.

The importance of infrared photodetectors cannot be overstated, especially in fields such as security, communication, and military. While silicon-based infrared photodetectors are widely used due to the maturity of the semiconductor industry, their band gap of 1.12 eV limits their infrared light absorption above 1100 nm, making them less effective. To overcome this limitation, we report a novel infrared photodetector prepared by growing graphene on the surface of zinc hyper-doped silicon. This technique utilizes hyper-doping to introduce deep level assisted infrared light absorption benefit from the enhanced carrier collection capacity of graphene. Without introducing new energy consumption, the hyper-doped substrate annealing treatment is completed during the growth of graphene. By the improvement of transport and collection of charge carriers, the graphene growth adjusts the band structure to upgrade electrode contact, resulting in a response of 1.6 mA W-1under laser irradiation with a wavelength of 1550 nm and a power of 2 mW. In comparison, the response of the photodetector without graphene was only 0.51 mA W-1, indicating a three-fold performance improvement. Additionally, the device has lower dark current and lower noise current, resulting in a noise equivalent power of 7.6 × 10-8W Hz-0.5. Thus, the combination of transition metal hyper-doping and graphene growth technology has enormous potential for developing the next generation of infrared photodetectors.

Dielectric Regulation for Efficient Top-Emission Perovskite Light-Emitting Diodes with Suppressed Efficiency Roll-off.

Perovskite light-emitting diodes (PeLEDs) have shown incalculable application potential in the fields of next-generation displays and light communication owing to the rapidly increased external quantum efficiencies (EQEs). However, most PeLEDs obtain a maximum EQE at small current density (J) region and suffer from severe efficiency roll-off in different extents. Herein, it is demonstrated that the dopant with large dipole moment like KBF4 facilitates the effective dielectric regulation of perovskite emissive layer. The increased dielectric constant lowers the exciton binding energy and suppresses the Auger recombination of the 2D/3D segregated perovskite structure, which improves the photoluminescence quantum yield remarkably at an excitation intensity up to 103  mW cm-2 . Accordingly, the top-emission PeLED that delivers a high maximum EQE above 20% is fabricated and can retain EQE > 10% at an extremely high J of 708 mA cm-2 . These results represent one of the most efficient top-emission PeLEDs with ultra-low efficiency roll-off, which provide a viable methodology for tuning the dielectric response of perovskite films for improved high radiance performance of perovskite electroluminescence devices.

Anti-reflection effect of high refractive index polyurethane with different light trapping structures on solar cells.

The textured surfaces to reduce light reflectivity by using acid-alkali chemical etching and SiNx films are generally necessary for commercial crystalline silicon solar cells. However, this etching process requires a large amount of environmentally harmful acid-alkali solution and has limited options for texture and size. To overcome these disadvantages, a new anti-reflection strategy is proposed in this study, which is using soft nanoimprint lithography to prepare the textured structures on the outside of the SiNx films. The polyurethane with a high refractive index of 1.64 is selected as the texture material, and different templates are selected to prepare it into different light trapping structures, including positive-inverted pyramids, inverted lace cones, and positive-inverted moth-eye nanostructures allowing for easy customization of the textured structures. The finite element simulation and experiments demonstrate that these light trapping structures have a wide spectrum anti-reflection performance in visible and near-infrared bands. With the back surface of the commercial passivated emitter rear contact (PERC) bi-facial solar cells as the imprint substrates, some light trapping structures can reduce the surface weighted average light reflectivity (Rw) at the band of 300-1200 nm from 18.31% to less than 10% and the optimal structures can reduce Rw to 8.71%. This anti-reflection strategy can also be applied to thin-film solar cells and crystalline silicon solar cells of other structures, such as HIT, Topcon, Perovskite/c-Si tandem, and so forth, which shows great development potential.

Self-evolved BOx anchored on Mg2B2O5 crystallites for high-performance oxidative dehydrogenation of propane.

Oxidative dehydrogenation of propane (ODHP) is a promising process for producing propene. Recently, some boron-based catalysts have exhibited excellent olefin selectivity in ODHP. However, their complex synthetic routes and poor stability under high-temperature reaction conditions have hindered their practical application. Herein, we report a self-evolution method rather than conventional assembly approaches to acquire structures with excellent stability under a high propane conversion, from a single precursor-MgB2. The catalyst feasibly prepared and optimized exhibited a striking performance: 60% propane conversion with a 43.2% olefin yield at 535°C. The BOx corona pinned by the strong interaction with the borate enabled zero loss of the high conversion (around 40%) and olefins selectivity (above 80%) for over 100 h at 520°C. This all-in-one strategy of deriving all the necessary components from just one raw chemical provides a new way to synthesize effective and economic catalysts for potential industrial implementation.

Lattice-Gradient Perovskite KTaO3 Films for an Ultrastable and Low-Dose X-Ray Detector.

Conventional indirect X-ray detectors employ scintillating phosphors to convert X-ray photons into photodiode-detectable visible photons, leading to low conversion efficiencies, low spatial resolutions, and optical crosstalk. Consequently, X-ray detectors that directly convert photons into electric signals have long been desired for high-performance medical imaging and industrial inspection. Although emerging hybrid inorganic-organic halide perovskites, such as CH3 NH3 PbI3 and CH3 NH3 PbBr3 , exhibit high sensitivity, they have salient drawbacks including structural instability, ion motion, and the use of toxic Pb. Here, this work reports an ultrastable, low-dose X-ray detector comprising KTaO3 perovskite films epitaxially grown on a Nb-doped strontium titanate substrate using a low-cost solution method. The detector exhibits a stable photocurrent under high-dose irradiation, high-temperature (200 °C), and aqueous conditions. Moreover, the prototype KTaO3 -film-based detector exhibits a 150-fold higher sensitivity (3150 µC Gyair -1 cm-2 ) and 150-fold lower detection limit (<40 nGyair s-1 ) than those of commercial α-Se-based direct detectors. Systematic investigations reveal that the high stability of the detector originates from the strong covalent bonds within the KTaO3 film, whereas the low detection limit is due to a lattice-gradient-driven built-in electric field and the high insulating property of KTaO3 film. This study unveils a new path toward the fabrication of green, stable, and low-dose X-ray detectors using oxide perovskite films, which have significant application potential in medical imaging and security operations.

Silicon-Nanomembrane-Based Broadband Synaptic Phototransistors for Neuromorphic Vision.

Neuromorphic vision has been attracting much attention due to its advantages over conventional machine vision (e.g., lower data redundancy and lower power consumption). Here we develop synaptic phototransistors based on the silicon nanomembrane (Si NM), which are coupled with lead sulfide quantum dots (PbS QDs) and poly(3-hexylthiophene) (P3HT) to form a heterostructure with distinct photogating. Synaptic phototransistors with optical stimulation have outstanding synaptic functionalities ranging from ultraviolet (UV) to near-infrared (NIR). The broadband synaptic functionalities enable an array of synaptic phototransistors to achieve the perception of brightness and color. In addition, an array of synaptic phototransistors is capable of simultaneous sensing, processing, and memory, which well mimics human vision.

Oriented nucleation in formamidinium perovskite for photovoltaics.

The black phase of formamidinium lead iodide (FAPbI3) perovskite shows huge promise as an efficient photovoltaic, but it is not favoured energetically at room temperature, meaning that the undesirable yellow phases are always present alongside it during crystallization1-4. This problem has made it difficult to formulate the fast crystallization process of perovskite and develop guidelines governing the formation of black-phase FAPbI3 (refs. 5,6). Here we use in situ monitoring of the perovskite crystallization process to report an oriented nucleation mechanism that can help to avoid the presence of undesirable phases and improve the performance of photovoltaic devices in different film-processing scenarios. The resulting device has a demonstrated power-conversion efficiency of 25.4% (certified 25.0%) and the module, which has an area of 27.83 cm2, has achieved an impressive certified aperture efficiency of 21.4%.

Insights into the Effect of SiO Particle Size on the Electrochemical Performance between Half and Full Cells for Li-Ion Batteries.

Silicon monoxide (SiO) has attracted growing attention as one of the most promising anodes for high-energy-density lithium-ion batteries (LIBs), benefiting from relatively low volume expansion and superior cycling performance compared to bare silicon (Si). However, the size of the SiO particle for commercial application remains uncertain. Besides, the materials and concepts developed on the laboratory level in half cells are quite different from what is necessary for practical operation in full cells. Herein, we investigate the electrochemical performance of SiO with different particle sizes between half cells and full cells. The SiO with larger particle size exhibits worse electrochemical performance in the half cell, whereas it demonstrates excellent cycling stability with a high capacity retention of 91.3% after 400 cycles in the full cell. The reasons for the differences in their electrochemical performance between half cells and full cells are further explored in detail. The SiO with larger particle size possessing superior electrochemical performance in full cells benefits from consuming less electrolyte and not being easier to aggregate. It indicates that the SiO with larger particle size is recommended for commercial application and part of the information provided from half cells may not be advocated to predict the cycling performances of the anode materials. The analysis based on the electrochemical performance of the SiO between half cells and full cells gives fundamental insight into further Si-based anode research.

Detector-grade perovskite single-crystal wafers via stress-free gel-confined solution growth targeting high-resolution ionizing radiation detection.

Solution-processed organic‒inorganic halide perovskite (OIHP) single crystals (SCs) have demonstrated great potential in ionizing radiation detection due to their outstanding charge transport properties and low-cost preparation. However, the energy resolution (ER) and stability of OIHP detectors still lag far behind those of melt-grown inorganic perovskite and commercial CdZnTe counterparts due to the absence of detector-grade high-quality OIHP SCs. Here, we reveal that the crystallinity and uniformity of OIHP SCs are drastically improved by relieving interfacial stress with a facial gel-confined solution growth strategy, thus enabling the direct preparation of large-area detector-grade SC wafers up to 4 cm with drastically suppressed electronic and ionic defects. The resultant radiation detectors show both a small dark current below 1 nA and excellent baseline stability of 4.0 × 10-8 nA cm-1 s-1 V-1, which are rarely realized in OIHP detectors. Consequently, a record high ER of 4.9% at 59.5 keV is achieved under a standard 241Am gamma-ray source with an ultralow operating bias of 5 V, representing the best gamma-ray spectroscopy performance among all solution-processed semiconductor radiation detectors ever reported.

Photo-Stimuli-Responsive Dual-Emitting Luminescence of a Spiropyran-Encapsulating Metal-Organic Framework for Dynamic Information Encryption.

The development of photo-stimuli-responsive luminescent materials is essential to address emerging demands in encryption security. Here, a novel photo-stimuli-responsive dual-emitting luminescent material ZJU-128⊃SP (SP = spiropyran) is reported, which is obtained by encapsulating spiropyran molecules into a cadmium-based metal-organic framework (MOF), [Cd3 (TCPP)2 ]·4DMF·4H2 O (ZJU-128, H4 TCPP = 2,3,5,6-tetrakis (4-carboxyphenyl)pyrazine). This MOF/dye composite ZJU-128⊃SP exhibits a blue emission from the ligand of ZJU-128 at 447 nm and a red emission around 650 nm from spiropyran. Utilizing the photoisomerization of spiropyran from ring-closed to ring-open form under UV-light irradiation, significant fluorescence resonance energy transfer (FRET) process between ZJU-128 and spiropyran is achieved. As a result, the blue emission of ZJU-128 is gradually decreased while the red emission of spiropyran increases. This dynamic fluorescent behavior can fully recover to the original state following exposure to visible light (>405 nm). By taking advantage of the time-dependent fluorescence, dynamical anti-counterfeiting patterns and multiplexed coding are successfully developed based on ZJU-128⊃SP film. This work provides an inspiring point for the design of information encryption materials with higher security requirements.

High-Performance and Self-Powered X-Ray Detectors Made of Smooth Perovskite Microcrystalline Films with 100†µm Grains.

Perovskite single crystals and polycrystalline films have complementary merits and deficiencies in X-ray detection and imaging. Herein, we report preparation of dense and smooth perovskite microcrystalline films with both merits of single crystals and polycrystalline films through polycrystal-induced growth and hot-pressing treatment (HPT). Utilizing polycrystalline films as seeds, multi-inch-sized microcrystalline films can be in situ grown on diverse substrates with maximum grain size reaching 100 µm, which endows the microcrystalline films with comparable carrier mobility-lifetime (µτ) product as single crystals. As a result, self-powered X-ray detectors with impressive sensitivity of 6.1×104  µC Gyair -1 cm-2 and low detection limit of 1.5 nGyair s-1 are achieved, leading to high-contrast X-ray imaging at an ultra-low dose rate of 67 nGyair s-1 . Combining with the fast response speed (186 µs), this work may contribute to the development of perovskite-based low-dose X-ray imaging.

Facile synthesis of defect-rich RuCu nanoflowers for efficient hydrogen evolution reaction in alkaline media.

Developing high-performance electrocatalysts toward hydrogen evolution reaction (HER) in alkaline media is highly desirable for industrial applications in the field of water splitting but is still challenging. Herein, we successfully synthesized RuCu nanoflowers (NFs) with tunable atomic ratios using a facile wet chemistry method. The Ru3Cu NFs need only 55 mV to achieve a current density of 10 mA cm-2, which shows ideal durability with only 4 mV decay after 2000 cycles, largely outperforming the catalytic properties of commercial Pt/C. The Ru3Cu NFs comprise many nanosheets that can provide more active sites for HER. In addition, the introduction of Cu can modulate the electronic structure of Ru, facilitate water dissociation, and optimize H adsorption/desorption ability. Thus, the flower-like structure together with the proper incorporation of Cu boosts HER performance.

Enhanced Optical and Electronic Properties of Silicon Nanosheets by Phosphorus Doping Passivation.

In this paper, we use the spin-on-dopant technique for phosphorus doping to improve the photoelectric properties of soft-chemical-prepared silicon nanosheets. It was found that the luminescence intensity and luminescence lifetime of the doped samples was approximately 4 fold that of the undoped samples, due to passivation of the surface defects by phosphorus doping. Meanwhile, phosphorus doping combined with high-temperature heat treatment can reduce the resistivity of multilayer silicon nanosheets by 6 fold compared with that of as-prepared samples. In conclusion, our work brings soft-chemical-prepared silicon nanosheets one step closer to practical application in the field of optoelectronics.