Perovskite spin light-emitting diodes with simultaneously high electroluminescence dissymmetry and high external quantum efficiency.

Realizing high electroluminescence dissymmetric factor and high external quantum efficiency at the same time is challenging in light-emitting diodes with direct circularly polarized emission. Here, we show that high electroluminescence dissymmetric factor and high external quantum efficiency can be simultaneously achieved in light-emitting diodes based on chiral perovskite quantum dots. Specifically, chiral perovskite quantum dots with chiral-induced spin selectivity can concurrently serve as localized radiative recombination centers of spin-polarized carriers for circularly polarized emission, thereby suppressing the relaxation of spins, Meanwhile, improving the chiral ligand exchange efficiency is found to synergistically promote their spin selectivity and optoelectronic properties so that chiroptoelectronic performance of resulting devices can be facilitated.

Mitigating the Efficiency Deficit in Single-Crystal Perovskite Solar Cells by Precise Control of the Growth Processes.

The power conversion efficiencies (PCEs) of polycrystalline perovskite solar cells (PC-PSCs) have now reached a plateau after a decade of rapid development, leaving a distinct gap from their Shockley-Queisser limit. To continuously mitigate the PCE deficit, nonradiative carrier losses resulting from defects should be further optimized. Single-crystal perovskites are considered an ideal platform to study the efficiency limit of perovskite solar cells due to their intrinsically low defect density, as demonstrated in bulk single crystals.

Perovskite Thin-Film Transistors for Ultra-Low-Voltage Neuromorphic Visions.

Perovskite thin-film transistors (TFTs) simultaneously possessing exceptional carrier transport capabilities, nonvolatile memory effects, and photosensitivity have recently attracted attention in fields of both complementary circuits and neuromorphic computing. Despite continuous performance improvements through additive and composition engineering of the channel materials, the equally crucial dielectric/channel interfaces of perovskite TFTs have remained underexplored. Here, it is demonstrated that engineering the dielectric/channel interface in 2D tin perovskite TFTs not only enhances the performance and operational stability for their utilization in complementary circuits but also enables efficient synaptic behaviors (optical information sensing and storage) under an extremely low operating voltage of -1 mV at the same time.

A platform for integrated spectrometers based on solution-processable semiconductors.

Acquiring real-time spectral information in point-of-care diagnosis, internet-of-thing, and other lab-on-chip applications require spectrometers with hetero-integration capability and miniaturized feature. Compared to conventional semiconductors integrated by heteroepitaxy, solution-processable semiconductors provide a much-flexible integration platform due to their solution-processability, and, therefore, more suitable for the multi-material integrated system. However, solution-processable semiconductors are usually incompatible with the micro-fabrication processes.

A fully integrated wearable ultrasound system to monitor deep tissues in moving subjects.

Recent advances in wearable ultrasound technologies have demonstrated the potential for hands-free data acquisition, but technical barriers remain as these probes require wire connections, can lose track of moving targets and create data-interpretation challenges. Here we report a fully integrated autonomous wearable ultrasonic-system-on-patch (USoP). A miniaturized flexible control circuit is designed to interface with an ultrasound transducer array for signal pre-conditioning and wireless data communication.

Stretchable ultrasonic arrays for the three-dimensional mapping of the modulus of deep tissue.

Serial assessment of the biomechanical properties of tissues can be used to aid the early detection and management of pathophysiological conditions, to track the evolution of lesions and to evaluate the progress of rehabilitation. However, current methods are invasive, can be used only for short-term measurements, or have insufficient penetration depth or spatial resolution. Here we describe a stretchable ultrasonic array for performing serial non-invasive elastographic measurements of tissues up to 4 cm beneath the skin at a spatial resolution of 0.

Ultrahigh-Q Lead Halide Perovskite Microlasers.

Lead halide perovskites have been promising platforms for micro- and nanolasers. However, the fragile nature of perovskites poses an extreme challenge to engineering a cavity boundary and achieving high-quality (Q) modes, severely hindering their practical applications. Here, we combine an etchless bound state in the continuum (BIC) and a chemically synthesized single-crystalline CsPbBr microplate to demonstrate on-chip integrated perovskite microlasers with ultrahigh Q factors.

A wearable cardiac ultrasound imager.

Continuous imaging of cardiac functions is highly desirable for the assessment of long-term cardiovascular health, detection of acute cardiac dysfunction and clinical management of critically ill or surgical patients. However, conventional non-invasive approaches to image the cardiac function cannot provide continuous measurements owing to device bulkiness, and existing wearable cardiac devices can only capture signals on the skin. Here we report a wearable ultrasonic device for continuous, real-time and direct cardiac function assessment.

Perovskite superlattices with efficient carrier dynamics.

Compared with their three-dimensional (3D) counterparts, low-dimensional metal halide perovskites (2D and quasi-2D; BAMX, such as B = R-NH, A = HC(NH), Cs; M = Pb, Sn; X = Cl, Br, I) with periodic inorganic-organic structures have shown promising stability and hysteresis-free electrical performance. However, their unique multiple-quantum-well structure limits the device efficiencies because of the grain boundaries and randomly oriented quantum wells in polycrystals. In single crystals, the carrier transport through the thickness direction is hindered by the layered insulating organic spacers.

High-performance hysteresis-free perovskite transistors through anion engineering.

Despite the impressive development of metal halide perovskites in diverse optoelectronics, progress on high-performance transistors employing state-of-the-art perovskite channels has been limited due to ion migration and large organic spacer isolation. Herein, we report high-performance hysteresis-free p-channel perovskite thin-film transistors (TFTs) based on methylammonium tin iodide (MASnI) and rationalise the effects of halide (I/Br/Cl) anion engineering on film quality improvement and tin/iodine vacancy suppression, realising high hole mobilities of 20 cm V s, current on/off ratios exceeding 10, and threshold voltages of 0 V along with high operational stabilities and reproducibilities. We reveal ion migration has a negligible contribution to the hysteresis of Sn-based perovskite TFTs; instead, minority carrier trapping is the primary cause.

Three-dimensional transistor arrays for intra- and inter-cellular recording.

Electrical impulse generation and its conduction within cells or cellular networks are the cornerstone of electrophysiology. However, the advancement of the field is limited by sensing accuracy and the scalability of current recording technologies. Here we describe a scalable platform that enables accurate recording of transmembrane potentials in electrogenic cells.

Continuous monitoring of deep-tissue haemodynamics with stretchable ultrasonic phased arrays.

Stretchable wearable devices for the continuous monitoring of physiological signals from deep tissues are constrained by the depth of signal penetration and by difficulties in resolving signals from specific tissues. Here, we report the development and testing of a prototype skin-conformal ultrasonic phased array for the monitoring of haemodynamic signals from tissues up to 14 cm beneath the skin. The device allows for active focusing and steering of ultrasound beams over a range of incident angles so as to target regions of interest.

A fabrication process for flexible single-crystal perovskite devices.

Organic-inorganic hybrid perovskites have electronic and optoelectronic properties that make them appealing in many device applications. Although many approaches focus on polycrystalline materials, single-crystal hybrid perovskites show improved carrier transport and enhanced stability over their polycrystalline counterparts, due to their orientation-dependent transport behaviour and lower defect concentrations. However, the fabrication of single-crystal hybrid perovskites, and controlling their morphology and composition, are challenging.

Frequency- and Power-Dependent Photoresponse of a Perovskite Photodetector Down to the Single-Photon Level.

Organometallic halide perovskites attract strong interests for their high photoresponsivity and solar cell efficiency. However, there was no systematic study of their power- and frequency-dependent photoresponsivity. We identified two different power-dependent photoresponse types in methylammonium lead iodide perovskite (MAPbI) photodetectors.

Strain engineering and epitaxial stabilization of halide perovskites.

Strain engineering is a powerful tool with which to enhance semiconductor device performance. Halide perovskites have shown great promise in device applications owing to their remarkable electronic and optoelectronic properties. Although applying strain to halide perovskites has been frequently attempted, including using hydrostatic pressurization, electrostriction, annealing, van der Waals force, thermal expansion mismatch, and heat-induced substrate phase transition, the controllable and device-compatible strain engineering of halide perovskites by chemical epitaxy remains a challenge, owing to the absence of suitable lattice-mismatched epitaxial substrates.

Monitoring of the central blood pressure waveform via a conformal ultrasonic device.

Continuous monitoring of the central-blood-pressure waveform from deeply embedded vessels, such as the carotid artery and jugular vein, has clinical value for the prediction of all-cause cardiovascular mortality. However, existing non-invasive approaches, including photoplethysmography and tonometry, only enable access to the superficial peripheral vasculature. Although current ultrasonic technologies allow non-invasive deep-tissue observation, unstable coupling with the tissue surface resulting from the bulkiness and rigidity of conventional ultrasound probes introduces usability constraints.

Stretchable ultrasonic transducer arrays for three-dimensional imaging on complex surfaces.

Ultrasonic imaging has been implemented as a powerful tool for noninvasive subsurface inspections of both structural and biological media. Current ultrasound probes are rigid and bulky and cannot readily image through nonplanar three-dimensional (3D) surfaces. However, imaging through these complicated surfaces is vital because stress concentrations at geometrical discontinuities render these surfaces highly prone to defects.

Controlled Homoepitaxial Growth of Hybrid Perovskites.

Organic-inorganic hybrid perovskites have demonstrated tremendous potential for the next-generation electronic and optoelectronic devices due to their remarkable carrier dynamics. Current studies are focusing on polycrystals, since controlled growth of device compatible single crystals is extremely challenging. Here, the first chemical epitaxial growth of single crystal CH NH PbBr with controlled locations, morphologies, and orientations, using combined strategies of advanced microfabrication, homoepitaxy, and low temperature solution method is reported.

An efficient one-pot synthesis of benzo[4,5]imidazo[1,2-a]quinoxalines via copper-catalyzed process.

A copper-catalyzed one-pot process for the construction of benzo[4,5]imidazo[1,2-a]quinoxalines under air is described. Aryl chlorides, aryl bromides, and aryl iodides can be applied to the synthesis of these compounds.