Fast-Response,Highly Air-Stable,and Water-Resistant Organic Photodetectors Based on a Single-Crystal Pt Complex

Organic semiconductors demonstrate several advantages over conventional inorganic materials for novel electronic and optoelectronic applications, including molecularly tunable properties, flexibility, low-cost, and facile device integration. However, before organic semiconductors can be used for the next-generation devices, such as ultrafast photodetectors (PDs), it is necessary to develop new materials that feature both high mobility and ambient stability. Toward this goal, a highly stable PD based on the organic single crystal [PtBr₂(5,5′-bis(CF₃CH₂OCH₂)-2,2′-bpy)] (or “Pt complex (1o)”) is demonstrated as the active semiconductor channel—a material that features a lamellar molecular structure and high-quality, intraligand charge transfer. Benefitting from its unique crystal structure, the Pt-complex (1o) device exhibits a field-effect mobility of ≈0.45 cm² V⁻¹ s⁻¹ without loss of significant performance under ambient conditions even after 40 days without encapsulation, as well as immersion in distilled water for a period of 24 h. Furthermore, the device features a maximum photoresponsivity of 1 × 10³ A W⁻¹, a detectivity of 1.1 × 10¹² cm Hz^1/2 W⁻¹, and a record fast response/recovery time of 80/90 µs, which has never been previously achieved in other organic PDs. These findings strongly support and promote the use of the single-crystal Pt complex (1o) in next-generation organic optoelectronic devices.     

Centimeter-Sized Single Crystals of Dion-Jacobson Phase Lead-Free Double Perovskite for Efficient X-ray Detection

2D Dion–Jacobson (DJ) phase hybrid perovskites have shown great promise in the photoelectronic field owing to their outstanding optoelectronic performance and superior structural rigidity. However, DJ phase lead-free double perovskites are still a virgin land with direct X-ray detection. Herein, we have designed and synthesized a new DJ phase lead-free layered double perovskite of (HIS)₂AgSbBr₈ ( 1 , HIS²⁺ = histammonium). Centimeter-sized (18 × 10 × 5 mm³) single crystals of 1 are successfully grown via the temperature cooling technique, exhibiting remarkable semiconductive characteristics such as a high resistivity (2.2 × 10¹¹ Ω cm), a low trap state density (3.56 × 10¹⁰ cm⁻³), and a large mobility-lifetime product (1.72 × 10⁻³ cm² V⁻¹). Strikingly, its single-crystal-based X-ray detector shows a high sensitivity of 223 µC Gy⁻¹_air cm⁻² under 33.3 V mm⁻¹, a low detection limit (84.2 nGy_airs⁻¹) and superior anti-fatigue. As far as we know, we firstly demonstrates the potential of 2D DJ phase lead-free hybrid double perovskite in X-ray detection, showing excellent photoelectric response and operational stability. This work will pave a promising pathway to the innovative application of hybrid perovskites for eco-friendly and efficient X-ray detection.     

Neutron flux measurements with a Li2B4O7 crystal

The effect of neutron irradiation on a lithium tetraborate (Li₂B₄O₇, LBO) single crystal has been investigated. The crystals of high optical quality are found to be quite stable under high neutron fluence. This study shows that LBO crystals can be used as a proportional counter for neutron fluxes of the order 10⁹ cm⁻² s⁻¹ and higher. The detectors fabricated were found to have a sensitivity of ∼3×10⁻¹⁸ A (nv)⁻¹.     

Additive-Enhanced Crystallization of Inorganic Perovskite Single Crystals for High-Sensitivity X-Ray Detection

Inorganic cesium lead halide perovskite single crystals are particularly intriguing to ionizing radiation detection by virtue of their material stability and high attenuation coefficients. However, the growth of high-quality inorganic perovskite single crystals remains challenging, mainly due to the limited solubility. In this work, an additive-enhanced crystallization method is proposed for cesium lead perovskites. The additive can remarkably increase the solubility of cesium bromide in dimethyl sulfoxide (DMSO) forming a balanced stoichiometric precursor solution, which prevents the formation of impurity phases. In addition, the additives would react with DMSO generating glyoxylic acid (GLA) via nucleophilic substitution and Kornblum oxidation reactions. The GLA can form stable PbBr₂-DMSO-GLA complexes, which enables better crystallinity, uniformity and much longer carrier lifetimes for the grown single crystals. The X-ray detectors using the additive-enhanced crystals exhibit an ultra-high sensitivity of 3.0 × 10⁴ µC Gy_air⁻¹ cm⁻² which is more than two orders of magnitude higher than that for the control devices.     

Growth of CuInTe2 single crystals by iodine transport and their characterization

The single crystals with stoichiometry close to 1:1:2 of CuInTe₂ (CIT) have been grown by chemical vapor transport (CVT) technique using iodine as the transporting agent at different growth temperatures. Single crystal X-ray diffraction studies have confirmed the chalcopyrite structure for the grown crystals and the volume of unit cell is found to be the same for the crystals grown at different conditions. Energy dispersive X-ray (EDAX) analysis of CIT single crystals grown shows almost the same stoichiometric compositions. Scanning electron microscope (SEM) analysis reveals kink, step and layer patterns on the surface of CIT single crystals depending on the growth temperatures. The optical absorption spectra of as-grown CIT single crystals grown at different conditions show that they have same band gap energies (1.0405 eV). Raman spectra exhibit a high intensity peak of A₁ mode at 123 cm^?1. Annealed at 473 K in nitrogen atmosphere for 40 h CIT single crystals have higher hole mobility (105.6 cm²V^?1s^?1₎ and hole concentration (23.28 × 10¹⁷ cm^?3) compared with values of hole mobility (63.69 cm² V^?1 s^?1) and hole concentration (6.99 × 10¹⁵ cm^?3) of the as-grown CIT single crystals.     

Preparation and characterization of Cd.95Mn.05Se single crystals

Homogeneous crystals of Cd_.95Mn_.05Se of high optical quality have been grown by a modified Bridgman method. Magnetic susceptibility measurements verify the uniform distribution of Mn(II) obtained after annealing at 600°C.Crystals grown in the presence of 5 atomic percent excess selenium showed high resistivity; the addition of 1 mg iodine to a 10 g charge resulted in n-type conductivity and a room-temperature carrier concentration of 2.9 × 10¹⁶ cm^?3. The Hall mobility of these crystals was approximately 290 cm² V^?1 sec^?1.     

Flexible Porous Organic Polymer Membranes for Protonic Field-Effect Transistors

Artificial transistors represent an ideal means for meeting the requirements in interfacing with biological systems. It is pivotal to develop new proton-conductive materials for the transduction between biochemical events and electronic signals. Herein, the first demonstration of a porous organic polymer membrane (POPM) as a proton-conductive material for protonic field-effect transistors is presented. The POPM is readily prepared through a thiourea-formation condensation reaction. Under hydrated conditions and at room temperature, the POPM delivers a proton mobility of 5.7 × 10⁻³ cm² V⁻¹ s⁻¹; the charge carrier densities are successfully modulated from 4.3 × 10¹⁷ to 14.1 × 10¹⁷ cm⁻³ by the gate voltage. This study provides a type of promising modular proton-conductive materials for bioelectronics application.     

Honeycomb RhI3 Flakes with High Environmental Stability for Optoelectronics

The emerging 2D layered transition metal trihalides (MX₃) have attracted extremely high interest given their exceptional structural and physical properties. Continuing to extend the library of 2D MX₃ is essential for exploring new physical phenomena and enabling new functionality. Herein, the optical and electrical properties and the photodetection behavior of atomically thin RhI₃ flakes exfoliated from bulk crystals are reported. This compound exhibits superior air and thermal stability, as well as thickness-dependent bandgap from 1.1 (18L) to 1.4 eV (2L). Field-effect transistors based on the few-layer RhI₃ flakes display n-type semiconducting behavior with competitive mobility of 2.5 cm² V⁻¹ s⁻¹ and ON/OFF current ratio of 4 × 10⁴. Importantly, the outstanding responsivity of 11.5 A W⁻¹ and high specific detectivity of 2 × 10¹⁰ Jones are recorded from the RhI₃ photodetectors under 980 nm illumination at room temperature in air. These findings indicate a variety of potential applications of atomically thin RhI₃ flakes in future 2D-material-based electronic and optoelectronic devices.     

General Spatial Confinement Recrystallization Method for Rapid Preparation of Thickness-Controllable and Uniform Organic Semiconductor Single Crystals

Organic semiconductor single crystals (OSSCs) are ideal materials for studying the intrinsic properties of organic semiconductors (OSCs) and constructing high-performance organic field-effect transistors (OFETs). However, there is no general method to rapidly prepare thickness-controllable and uniform single crystals for various OSCs. Here, inspired by the recrystallization (a spontaneous morphological instability phenomenon) of polycrystalline films, a spatial confinement recrystallization (SCR) method is developed to rapidly (even at several second timescales) grow thickness-controllable and uniform OSSCs in a well-controlled way by applying longitudinal pressure to tailor the growth direction of grains in OSCs polycrystalline films. The relationship between growth parameters including the growth time, temperature, longitudinal pressure, and thickness is comprehensively investigated. Remarkably, this method is applicable for various OSCs including insoluble and soluble small molecules and polymers, and can realize the high-quality crystal array growth. The corresponding 50 dinaphtho[2,3-b:2″,3″-f]thieno[3,2-b]thiophene (DNTT) single crystals coplanar OFETs prepared by the same batch have the mobility of 4.1 ± 0.4 cm² V⁻¹ s⁻¹, showing excellent uniformity. The overall performance of the method is superior to the reported methods in term of growth rate, generality, thickness controllability, and uniformity, indicating its broad application prospects in organic electronic and optoelectronic devices.     

Van der Waals Epitaxial Growth of Atomic Layered HfS2 Crystals for Ultrasensitive Near‐Infrared Phototransistors

As a member of the group IVB transition metal dichalcogenides (TMDs) family, hafnium disulfide (HfS₂) is recently predicted to exhibit higher carrier mobility and higher tunneling current density than group VIB (Mo and W) TMDs. However, the synthesis of high‐quality HfS₂ crystals, sparsely reported, has greatly hindered the development of this new field. Here, a facile strategy for controlled synthesis of high‐quality atomic layered HfS₂ crystals by van der Waals epitaxy is reported. Density functional theory calculations are applied to elucidate the systematic epitaxial growth process of the S‐edge and Hf‐edge. Impressively, the HfS₂ back‐gate field‐effect transistors display a competitive mobility of 7.6 cm² V^?1 s^?1 and an ultrahigh on/off ratio exceeding 10⁸. Meanwhile, ultrasensitive near‐infrared phototransistors based on the HfS₂ crystals (indirect bandgap ≈1.45 eV) exhibit an ultrahigh responsivity exceeding 3.08 × 10⁵ A W^?1, which is 10⁹‐fold higher than 9 × 10^?5 A W^?1 obtained from the multilayer MoS₂ in near‐infrared photodetection. Moreover, an ultrahigh photogain exceeding 4.72 × 10⁵ and an ultrahigh detectivity exceeding 4.01 × 10¹² Jones, superior to the vast majority of the reported 2D‐materials‐based phototransistors, imply a great promise in TMD‐based 2D electronic and optoelectronic applications.     

A 1300 mm2 Ultrahigh‐Performance Digital Imaging Assembly using High‐Quality Perovskite Single Crystals

By fine‐tuning the crystal nucleation and growth process, a low‐temperature‐gradient crystallization method is developed to fabricate high‐quality perovskite CH₃NH₃PbBr₃ single crystals with high carrier mobility of 81 ± 5 cm² V^?1 s^?1 (>3 times larger than their thin film counterpart), long carrier lifetime of 899 ± 127 ns (>5 times larger than their thin film counterpart), and ultralow trap state density of 6.2 ± 2.7 × 10⁹ cm^?3 (even four orders of magnitude lower than that of single‐crystalline silicon wafers). In fact, they are better than perovskite single crystals reported in prior work: their application in photosensors gives superior detectivity as high as 6 × 10¹³ Jones, ≈10–100 times better than commercial sensors made of silicon and InGaAs. Meanwhile, the response speed is as fast as 40 µs, ≈3 orders of magnitude faster than their thin film devices. A large‐area (≈1300 mm²) imaging assembly composed of a 729‐pixel sensor array is further designed and constructed, showing excellent imaging capability thanks to its superior quality and uniformity. This opens a new possibility to use the high‐quality perovskite single‐crystal‐based devices for more advanced imaging sensors.     

Crystallized Monolayer Semiconductor for Ohmic Contact Resistance,High Intrinsic Gain,and High Current Density

The contact resistance limits the downscaling and operating range of organic field-effect transistors (OFETs). Access resistance through multilayers of molecules and the nonideal metal/semiconductor interface are two major bottlenecks preventing the lowering of the contact resistance. In this work, monolayer (1L) organic crystals and nondestructive electrodes are utilized to overcome the abovementioned challenges. High intrinsic mobility of 12.5 cm² V⁻¹ s⁻¹ and Ohmic contact resistance of 40 Ω cm are achieved. Unlike the thermionic emission in common Schottky contacts, the carriers are predominantly injected by field emission. The 1L-OFETs can operate linearly from V_DS = −1 V to V_DS as small as −0.1 mV. Thanks to the good pinch-off behavior brought by the monolayer semiconductor, the 1L-OFETs show high intrinsic gain at the saturation regime. At a high bias load, a maximum current density of 4.2 µA µm⁻¹ is achieved by the only molecular layer as the active channel, with a current saturation effect being observed. In addition to the low contact resistance and high-resolution lithography, it is suggested that the thermal management of high-mobility OFETs will be the next major challenge in achieving high-speed densely integrated flexible electronics.     

Red-Carbon-Quantum-Dot-Doped SnO2 Composite with Enhanced Electron Mobility for Efficient and Stable Perovskite Solar Cells

An efficient electron transport layer (ETL) plays a key role in promoting carrier separation and electron extraction in planar perovskite solar cells (PSCs). An effective composite ETL is fabricated using carboxylic-acid- and hydroxyl-rich red-carbon quantum dots (RCQs) to dope low-temperature solution-processed SnO₂, which dramatically increases its electron mobility by ≈20 times from 9.32 × 10⁻⁴ to 1.73 × 10⁻² cm² V⁻¹ s⁻¹. The mobility achieved is one of the highest reported electron mobilities for modified SnO₂. Fabricated planar PSCs based on this novel SnO₂ ETL demonstrate an outstanding improvement in efficiency from 19.15% for PSCs without RCQs up to 22.77% and have enhanced long-term stability against humidity, preserving over 95% of the initial efficiency after 1000 h under 40–60% humidity at 25 °C. These significant achievements are solely attributed to the excellent electron mobility of the novel ETL, which is also proven to help the passivation of traps/defects at the ETL/perovskite interface and to promote the formation of highly crystallized perovskite, with an enhanced phase purity and uniformity over a large area. These results demonstrate that inexpensive RCQs are simple but excellent additives for producing efficient ETLs in stable high-performance PSCs as well as other perovskite-based optoelectronics.     

Mixed Lead Halide Passivation of Quantum Dots

Infrared‐absorbing colloidal quantum dots (IR CQDs) are materials of interest in tandem solar cells to augment perovskite and cSi photovoltaics (PV). Today's best IR CQD solar cells rely on the use of passivation strategies based on lead iodide; however, these fail to passivate the entire surface of IR CQDs. Lead chloride passivated CQDs show improved passivation, but worse charge transport. Lead bromide passivated CQDs have higher charge mobilities, but worse passivation. Here a mixed lead‐halide (MPbX) ligand exchange is introduced that enables thorough surface passivation without compromising transport. MPbX–PbS CQDs exhibit properties that exceed the best features of single lead‐halide PbS CQDs: they show improved passivation (43 ± 5 meV vs 44 ± 4 meV in Stokes shift) together with higher charge transport (4 × 10^‐2 ± 3 × 10^‐3 cm² V^‐1 s^‐1 vs 3 × 10^‐2 ± 3 × 10^‐3 cm² V^‐1 s^‐1 in mobility). This translates into PV devices having a record IR open‐circuit voltage (IR V_oc) of 0.46 ± 0.01 V while simultaneously having an external quantum efficiency of 81 ± 1%. They provide a 1.7× improvement in the power conversion efficiency of IR photons (>1.1 µm) relative to the single lead‐halide controls reported herein.     

2D Ca3Sn2S7 Chalcogenide Perovskite: A Graphene‐Like Semiconductor with Direct Bandgap 0.5 eV and Ultrahigh Carrier Mobility 6.7 × 104 cm2 V−1 s−1

Graphene, a star 2D material, has attracted much attention because of its unique properties including linear electronic dispersion, massless carriers, and ultrahigh carrier mobility (10⁴–10⁵ cm² V^?1 s^?1). However, its zero bandgap greatly impedes its application in the semiconductor industry. Opening the zero bandgap has become an unresolved worldwide problem. Here, a novel and stable 2D Ruddlesden–Popper‐type layered chalcogenide perovskite semiconductor Ca₃Sn₂S₇ is found based on first‐principles GW calculations, which exhibits excellent electronic, optical, and transport properties, as well as soft and isotropic mechanical characteristics. Surprisingly, it has a graphene‐like linear electronic dispersion, small carrier effective mass (0.04 m₀), ultrahigh room‐temperature carrier mobility (6.7 × 10⁴ cm² V^?1 s^?1), Fermi velocity (3 × 10⁵ m s^?1), and optical absorption coefficient (10⁵ cm^?1). Particularly, it has a direct quasi‐particle bandgap of 0.5 eV, which realizes the dream of opening the graphene bandgap in a new way. These results guarantee its application in infrared optoelectronic and high‐speed electronic devices.     

Electrical properties of In<Subscript>2</Subscript>Se<Subscript>3</Subscript> layered crystals doped with cadmium,iodine, or copper

The electrical properties of nominally undoped and doped (0.1 wt % Cd, I, and Cu) In₂Se₃ single crystals have been studied in the range 80–400 K. Only iodine doping has been found to have a significant effect on the carrier concentration in In₂Se₃, raising it from 4.9 × 10¹⁷ to 1.6 × 10¹⁸ cm^?3 at 300 K. The observed temperature variation of in-plane electron mobility is interpreted in terms of acoustic phonon and neutral impurity scattering. The three dopants have the strongest effect on the out-of-plane conductivity of In₂Se₃.     

Bulk GaN layers grown on oxidized silicon by vapor-phase epitaxy in a hydride-chloride system

Bulk GaN layers with a thickness of up to 1.5 mm and a lateral size of 50 mm were grown by hydride-chloride vapor-phase epitaxy (HVPE). The best samples show a half-width (FWHM) of the X-ray rocking curve of ω_θ=27′, a charge carrier density of ∼8 × 10¹⁹ cm⁻³, and a mobility of ∼50 cm²/(V s). The photoluminescence spectra of the obtained epitaxial GaN layers exhibit an edge emission band at 348 eV. The HVPE layers are characterized by a high mechanical strength: H _V = 14 GPa.     

Anisotropy in the electrical properties of zirconium doped α -Fe2O3 single crystals

The electrical properties of zirconium doped α -Fe₂O₃ single crystals have been investigated from 470 up to 1300 K.As for the pure crystal, an anisotropy appears for the conductivity between the [001] direction and the (001) plane, although lowered by the dopant.Combining the results of electrical conductivity, thermoelectric power and complex impedance measurements, it was established that there was no significant kinetic contribution of the electrons and that their mobility was lower than a few tenths of cm²V⁻¹s⁻¹.     

Organic field-effect transistors using perylene

Organic thin-film field-effect transistors using organic semiconductor, perylene are fabricated, and electrical measurements are performed. The field-effect mobility of the device using perylene shows only p-type behavior while the electron and hole mobilities of its single crystal form are 5.5 and 0.5 cm²/V s, respectively. Stacked layers of perlyene (a layer fabricated with low deposition rate followed by another layer with high deposition rate) are formed for the active layer. Furthermore, hexadecafluorocopperphthalocyanine (F₁₆CuPc) and pentacene buffer layers are also used to modify the interface. For all of these devices, perylene layers acts as p-type. Electron trapping at grain boundaries and interface is thought to be a crucial factor. Hole mobility of 3.9×10⁻⁴ cm²/V s is obtained for the perylene film field-effect transistor device.     

Influence of W5+ ions on the optical properties of doped Bi12TiO20

There have been studied single crystals of undoped and doped Bi₁₂TiO₂₀ with two concentrations of W⁵⁺ (2.62 × 10¹⁷ cm⁻³ and 2.62 × 10¹⁸ cm⁻³). There have been obtained absorption spectra in the energy range of 10,482–15,408 cm⁻¹ by classical measurements. There have been determined the cross-section (σ_a) of the impurity absorption and the oscillator strength of d–d transitions. There have been calculated the refractive index of doped crystals and the concentration of Ti³⁺ ions in an undoped sample through an experiment.