Carrier Transport Capability Research Articles

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 -1mV at the same time. The interface-engineered TFT arrays operating at -1mV are then demonstrated as the preprocessing hardware for neuromorphic visions with pattern recognition accuracy of 92.2% and long-term memory capability. Such a low operating voltage provides operational feasibility to the design of large-scale-integrated and wearable/implantable neuromorphic hardware.

Tunable electronic and optical properties of a type-II GaP/SiH van der Waals heterostructure as photocatalyst: A first-principles study

In this study, a novel GaP/SiH heterostructure was successfully predicted and constructed. Subsequently, an in-depth and systematic investigation was conducted to explore its structural, electronic, transport and optical properties. The calculated structural performance results revealed that the GaP/SiH heterostructure was a typical type-II van der Waals heterostructure, exhibiting excellent energy stability, mechanical stability and thermodynamic stability. In particular, the formation of the GaP/SiH heterostructure significantly reduced the bandgap of the materials to 2.24eV, and the type-II energy band arrangement effectively suppressed the recombination of photogenerated carriers. Furthermore, the biaxial and vertical strains could finely modulate the electronic structure of the GaP/SiH heterojunction. The electron mobility of the GaP/SiH heterostructure was measured to be 1573.91 cm2 V⁻1 s⁻1, indicating its superior charge carrier transport capabilities. Meanwhile, the GaP/SiH heterostructure also exhibited excellent optical absorption performance in the visible and UV region up to 2.34 × 106 cm−1. Thus, the GaP/SiH heterostructure will be a strong candidate for photocatalytic applications due to its excellent light absorption properties, electrical properties, and stability.

Large-Area Perovskite Solar Module Produced by Introducing Self-Assembled L-Histidine Monolayer at TiO2 and Perovskite Interface.

Perovskite solar cells have been proven to enhance cell characteristics by introducing passivation materials that suppress defect formation. Defect states between the electron transport layer and the absorption layer reduce electron extraction and carrier transport capabilities, leading to a significant decline in device performance and stability, as well as an increased probability of non-radiative recombination. This study proposes the use of an amino acid (L-Histidine) self-assembled monolayer material between the transport layer and the perovskite absorption layer. Surface analysis revealed that the introduction of L-Histidine improved both the uniformity and roughness of the perovskite film surface. X-ray photoelectron spectroscopic analysis showed a reduction in oxygen vacancies in the lattice and an increase in Ti4+, indicating that L-Histidine successfully passivated trap states at the perovskite and TiO2 electron transport layer interface. In terms of device performance, the introduction of L-Histidine significantly improved the fill factor (FF) because the reduction in interface defects could suppress charge accumulation and reduce device hysteresis. The FF of large-area solar modules (25 cm2) with L-Histidine increased from 55% to 73%, and the power conversion efficiency (PCE) reached 16.5%. After 500 h of aging tests, the PCE still maintained 91% of its original efficiency. This study demonstrates the significant impact of L-Histidine on transport properties and showcases its potential for application in the development of large-area perovskite module processes.

Thermally activated delayed fluorescence dendrimers with strategic dendrons to construct highly efficient solution-processed OLEDs

For the promising merits of the precise molecular structures and the satisfactory dissolvability, Thermally activated delayed fluorescence (TADF) dendrimers are turning into the attractive candidates for fully solution-processed organic light-emitting diodes (OLEDs). However, the rational design of TADF dendrimers with strategic dendrons for improving the efficiency and decreasing efficiency roll-off is still challenging. Here, two TADF dendrimers, (4S,5R)-2,4,5,6-tetrakis(4-((6-((9-(3-(9H-carbazol-9-yl)phenyl)-9H-carbazol-3-yl)oxy)hexyl)oxy)-9H-carbazol-9-yl)isophthalonitrile (G-O-mCP) and (4S,5R)-2,4,5,6-tetrakis(4-((6-(3,5-bis(1-phenyl-1H-benzo[d]imidazol-2-yl)phenoxy)hexyl)oxy)-9H-carbazol-9-yl)isophthalonitrile (G-O-DPBi) were developed and synthesized by integrating the peripheral strategic dendrons with the emissive core through nonconjugated alkoxy chains. Impressively, the peripheral dendron of G-O-mCP possessing the superior hole-transporting capability belongs to the electron-donor category and the peripheral dendron of G-O-DPBi with the admirable electron-transporting capability belongs to the electron-acceptor category. The elaborate regulation of the different dendrons with solubilizing groups is beneficial for restraining the aggregation-caused quenching (ACQ) effect and balancing the carrier transport capability. Consequently, the fully solution-processed device based on G-O-mCP realized the maximum external quantum efficiency (EQE) of 19.98 %. In addition, the formation of the interfacial exciplex endows the solution-processed device with a extremely low turn-on voltage (Von) of 2.7 V and a high power efficiency (PE) of 43.80 lm/W, which is among the highest power efficiency of the reported TADF-OLEDs.

Novel bipolar host materials based on benzimidazole-hybridized phenanthridine for efficient red PhOLEDs

In this work, two innovative bipolar host materials, TPA-BIP and Cz-BIP, were designed and synthesized based on benzimidazole-hybridized phenanthridine (BIP) moiety as the electron transport unit. Compared to the widely used electronic transport unit benzimidazole, the BIP unit possesses a large planar rigid structure that can effectively enhance the thermal stability and the electron transfer capability of materials. Both materials exhibit good thermal stability respectively with Tg of 113 °C and 141 °C, proper HOMO/LUMO energy levels, and balance carrier transport capabilities. The red phosphorescent organic light-emitting diode prepared based on both materials achieve relatively high luminescence efficiency and relatively low efficiency roll-off. In particular, the EQEmax of the R1 device using TPA-BIP as the host material reaches 21.5 %, which is more superior than that of the conventional host material CBP (EQEmax of 9.84 %). Even at 1000 cd/m2, the device still achieves an EQE of 21.3 % with virtually no decrease. In conclusion, the results demonstrate the broad development potential of these BIP-based host materials for red PhOLEDs applications.

Physical performances for six novel Si allotropes in hexagonal 15 and 18 stacking orders

Elevating visible light absorption and carrier transport capacity of diamond silicon is a terrifying challenge for improving photoelectric conversion efficiency. Here, six new crystals with similar stacking patterns but various arrangement orders to Si–I are predicated by the random approach combined with group and graph theories. Considering potential applications in the photovoltaic field, we have conducted a detailed study on the stability and physical properties of these structures by first-principles calculations. As a result, these new structures meet mechanical, dynamic, and thermodynamic stabilities, and they are all indirect band gap semiconductor. In particular, among these materials, the effective mass of the smallest hole is only 0.11m0, which is smaller than that of diamond silicon. This result indicates that these structures have better carrier transport capabilities than diamond. In addition, XRD patterns of these six structures were studied for shedding more light for developing these structures in the experiment.

Achieving High Operating-Temperature Self-powered X-Ray Detection in Multilayered Hybrid Perovskites through Arylamine Intercalation.

Polar metal halide hybrid perovskites (PHPs) that exhibit outstanding bulk photovoltaic effect (BPVE), excellent semiconductor features, and strong radiation absorption ability, have shown prominent advantages in highly sensitive direct X-ray detection. However, it is still a challenge to explore PHPs with high BPVE temperature ranges, answering the demand of developing thermally stable passive X-ray detection. Herein, by intercalating arylamine into lead tribromide and inducing order-disorder phase transition, a 2D multilayered PHPs (BZA)2(MA)Pb2Br7 (BZPB, BZA = benzylamine, MA = methylamine) is synthesized. BZPB crystallizes in a polar space group Aea2 at a low-temperature phase and demonstrates a significant open-circuit of 0.3V deriving from BPVE under X-ray irradiation. Meanwhile, the strong X-ray absorption coefficient and outstanding carrier transport capability of the bilayered lead halide framework associated with the polar BPVE give BZPB excellent X-ray detection abilities. At 0V bias, the impressive sensitivity of BZPB is 98 µC Gy-1 cm-2. Importantly, the introduction of the rigid BZA ring increases the energy barrier of phase transition and thus dramatically enhances the X-ray detection operating temperature of BZPB up to 409 K without significant performance degradation. This work strongly reveals the great potential of rational design of metal halide hybrid perovskites for X-ray detection applications.

Electrical Double-Layer Transistors Comprising Block Copolymer Electrolytes for Low-Power-Consumption Photodetectors.

Electrical double-layer transistors (EDLTs) have received extensive research attention owing to their exciting advantages of low working voltage, high biocompatibility, and sensitive interfacial properties in ultrasensitive portable sensing applications. Therefore, it is of great interest to reduce photodetectors' operating voltage and power consumption by utilizing photo-EDLT. In this study, a series of block copolymers (BCPs) of poly(4-vinylpyridine)-block-poly(ethylene oxide) (P4VP-b-PEO) with different compositions were applied to formulate polyelectrolyte with indigo carmine salt in EDLT. Accordingly, PEO conduces ion conduction in the BCP electrolyte and enhances the carrier transport capability in the semiconducting channel; P4VP boosts the photocurrent by providing charge-trapping sites during light illumination. In addition, the severe aggregation of PEO is mitigated by forming a BCP structure with P4VP, enhancing the stability and photoresponse of the photo-EDLT. By optimizing the BCP composition, EDLT comprising P4VP16k-b-PEO5k and indigo carmine provides the highest specific detectivity of 2.1 × 107 Jones, along with ultralow power consumptions of 0.59 nW under 450 nm light illumination and 0.32 pW under dark state. The results indicate that photo-EDLT comprising the BCP electrolyte is a practical approach to reducing phototransistors' operating voltage and power consumption.

Acceptor-σ-donor-σ-acceptor host material for red phosphorescent and thermally activated delayed fluorescent OLEDs

A novel bipolar host molecule di-spiro [fluorene-9,5′-quinolino [3,2,1-de] acridine-9′,9″-fluorene]-2,2″,7,7″-tetracarbonitrile (QACN) featuring an Acceptor-σ-Donor-σ-Acceptor structure was developed. Systematic investigations into its photophysical, electrochemical, and thermal properties unveiled exceptional thermal stability, a three-dimensional spatial configuration, and bipolar carrier transport capability. Employing QACN as the host material in red phosphorescent and thermally activated delayed fluorescent (TADF) organic light-emitting diodes (OLEDs) yielded a maximum external quantum efficiency of 25.3 % and 16.5 %, respectively. Compared with the commercial material TPBi (EQE = 12.0 %, λEL = 668 nm) and mCP (EQE = 14.5 %, λEL = 652 nm), the TADF OLEDs based on QACN achieved a higher EQE and a large red-shift emission (EQE = 16.5 %, λEL = 694 nm). These findings underscore the potential of QACN as an effective host material for red phosphorescent and TADF emitters and provide a new auxiliary finesse for realizing deep red and near-infrared (NIR) OLEDs.

Universal growth of perovskite thin monocrystals from high solute flux for sensitive self-driven X-ray detection

Metal-halide perovskite thin monocrystals featuring efficient carrier collection and transport capabilities are well suited for radiation detectors, yet their growth in a generic, well-controlled manner remains challenging. Here, we reveal that mass transfer is one major limiting factor during solution growth of perovskite thin monocrystals. A general approach is developed to overcome synthetic limitation by using a high solute flux system, in which mass diffusion coefficient is improved from 1.7×10–10 to 5.4×10–10 m2 s–1 by suppressing monomer aggregation. The generality of this approach is validated by the synthesis of 29 types of perovskite thin monocrystals at 40–90 °C with the growth velocity up to 27.2 μm min–1. The as-grown perovskite monocrystals deliver a high X-ray sensitivity of 1.74×105 µC Gy−1 cm−2 without applied bias. The findings regarding limited mass transfer and high-flux crystallization are crucial towards advancing the preparation and application of perovskite thin monocrystals.

Nonstoichiometric In–S group yielding efficient carrier transfer pathway in In2S3 photoanode for solar water oxidation

AbstractThe construction of high‐efficiency photoanodes is essential for developing outstanding photoelectrochemical (PEC) water splitting cells. Furthermore, insufficient carrier transport capabilities and sluggish surface water oxidation kinetics limit its application. Using a solvothermal annealing strategy, we prepared a nonstoichiometric In–S (NS) group on the surface of an In2S3 photoanode in situ and unexpectedly formed a type II transfer path of carrier, thereby reducing the interfacial recombination and promoting the bulk separation. First‐principles calculations and comprehensive characterizations demonstrated NS group as an excellent oxygen evolution cocatalyst (OEC) that effectively facilitated carrier transport, lowered the surface overpotential, increased the surface active site, and accelerated the surface oxygen evolution reaction kinetics by precisely altering the rate‐determining steps of * to *OH and *O to *OOH. These synergistic effects remarkably enhanced the PEC performance, with a high photocurrent density of 5.02 mA cm−2 at 1.23 V versus reversible hydrogen electrode and a negative shift in the onset potential by 310 mV. This work provides a new strategy for the in situ preparation of high‐efficiency OECs and provides ideas for constructing excellent carrier transfer and transport channels.

Grain boundary passivation by alkylammonium salt for highly stable perovskite solar cells

Perovskite solar cells (PSCs) are a strong candidate for next-generation photovoltaics, but their long-term stability poses challenges for use as a future renewable energy source. In particular, ambient moisture causes detrimental effects on not only the stability but also performance of PSCs. Herein, alkylammonium salts with perfluorinated long alkyl chains are introduced to passivate the grain boundaries and form hydrophobic surfaces. The perfluorinated alkyl chain moiety introduced into the perovskite layer reduces defect density and suppresses nonradiative recombination, thereby enhancing carrier transport capability and achieving a power conversion efficiency (PCE) of 20.31 %. Given the hydrophobic effects of fluorinated compounds on PSCs, about 90 % of the initial PCE can be retained after 1,000 h of continuous operation under a relative humidity of ∼ 40 % without encapsulation. The proposed additive strategy thus enables long-term operational stability of PSCs under humid conditions.

Element Diffusion Induced Carrier Transport Enhancement in High-Performance CZTSSe Self-Powered Photodetector.

Cu2ZnSn(S,Se)4 (CZTSSe) has attracted great interest in thin-film solar cells due to its excellent photoelectric performance in past decades, and recently is gradually expanding to the field of photodetectors. Here, the CZTSSe self-powered photodetector is prepared by using traditional photovoltaic device structure. Under zero bias, it exhibits the excellent performance with a maximum responsivity of 0.77 A W-1, a high detectivity of 8.78 × 1012 Jones, and a wide linear dynamic range of 103dB. Very fast response speed with the rise/decay times of 0.576/1.792 µs, and ultra-high switching ratio of 3.54 × 105 are obtained. Comprehensive electrical and microstructure characterizations confirm that element diffusion among ITO, CdS, and CZTSSe layers not only optimizes band alignment of CdS/CZTSSe, but also suppresses the formation of interface defects. Such a suppression of interface defects and spike-like band alignment significantly inhibit carrier nonradiative recombination at interface and promote carrier transport capability. The low trap density in CZTSSe and low back contact barrier of CZTSSe/Mo could be responsible for the very fast response time of photodetector. This work definitely provides guidance for designing a high performance self-powered photodetector with high photoresponse, high switching ratio, fast response speed, and broad linear dynamic range.

Carrier mobility in doped Sb<sub>2</sub>Se<sub>3</sub> based on deformation potential theory

Antimony selenide (Sb<sub>2</sub>Se<sub>3</sub>) is an element-rich, cost-effective, and non-toxic material used as an absorber layer in solar cells. The performance of solar cells is significantly influenced by the transport characteristics of charge carriers. However, these characteristics in Sb<sub>2</sub>Se<sub>3</sub> have not been well understood. In this work, through density functional theory and deformation potential theory, we investigate the hole transport properties of pure Sb<sub>2</sub>Se<sub>3</sub> and As-, Bi-doped Sb<sub>2</sub>Se<sub>3</sub>. The incorporation of as element and Bi element does not introduce additional impurity levels within the band gap. However, the band gaps are reduced in both As-Sb<sub>2</sub>Se3 and Bi-Sb<sub>2</sub>Se<sub>3</sub> due to the band shifts of energy levels. This phenomenon is primarily attributed to the interactions between the unoccupied 4p and 6p states of the doping atoms and the unoccupied 4p states of Se atoms, as well as the unoccupied 5p states of Sb atoms. In this study, we calculate and analyze three key parameters affecting mobility: effective mass, deformation potential, and elastic constants. The results indicate that effective mass has the greatest influence on mobility, with Bi-Sb<sub>2</sub>Se<sub>3</sub> exhibiting the highest average mobility. The average effective mass is highest in As-Sb<sub>2</sub>Se<sub>3</sub> and lowest in Bi-Sb<sub>2</sub>Se<sub>3</sub>. The elastic constants of the As- and Bi-doped Sb<sub>2</sub>Se<sub>3</sub> structures show minimal differences compared with that of the intrinsic Sb<sub>2</sub>Se<sub>3</sub> structure. By comparing the intrinsic, As-doped, and Bi-doped Sb<sub>2</sub>Se<sub>3</sub>, it is evident that doping has a minor influence on deformation potential energy along various directions. The study reveals that the hole mobility in Sb<sub>2</sub>Se<sub>3</sub> displays significant anisotropy, with higher mobilities observed in the <i>x</i>-direction and the <i>y</i>-direction than in the <i>z</i>-direction. This discrepancy is attributed to stronger covalent bonding primarily in the <i>x</i>- and <i>y</i>-direction, while in the <i>z</i>-direction weaker van der Waals forces is dominant. The directions with enhanced charge carrier transport capability contribute to efficient transfer and collection of photo-generated charge carriers. Therefore, our research theoretically underscores the significance of controlling the growth of antimony selenide along specific directions.

MIL-101-derived porous WO3/FeWO4 hierarchical structures with efficient heterojunction interfaces for excellent room temperature n-butanol-sensing performance

This study originally reports the in-situ construction of porous WO3/FeWO4 ribbon-like hierarchical composites with unique and intense heterojunction interface behavior and the enhanced adsorption and carrier transport capability for effectively detecting n-butanol at room temperature. The introduction of different adding amounts of MIL-101 plays the key role of the morphological evolution of WO3-based microstructures with the well-distributed nanoparticles in situ growth on the surface by a facile electrospinning and subsequent calcination process. Compared with pristine WO3, a sharp and useful reduction of the optimal operating temperature from 220 to 25 °C can be observed as the Fe component increasing, mainly owing to the inverted p-type gas sensitive response caused by the controllable variable of FeWO4 phase in the multiple effective WO3-FeWO4 heterojunctions. The optimal WO3/FeWO4 composites can display the highest response of 12.3 and a relatively short response/recovery times of 110/140 s to 100 ppm n-butanol at 25 °C, together with the superior gas selectivity, repeatability, humidity and long-term stability. Density functional theory (DFT) simulation is employed for verifying the significant adsorption interaction and charge transfer between n-butanol molecule and WO3/FeWO4. Regular distribution of WO3-FeWO4 heterojunction interfaces can not only determine the collaborative modulation of electronic structures, but also provide the efficient surface/interface transport mechanism for MIL-101 induced one-dimensional (1D) hierarchical ribbons. Actually, the integrated gas-sensitive components based on WO3/FeWO4 composites exhibit the rapid response characteristic under room temperature condition and provide a friendly strategy of optimizing the practical detection of ppm-level n-butanol for other inorganic heterogeneous sensors.

Dimensional and Optoelectronic Tuning of Lead-free Perovskite Cs3 Bi2 I9-n Brn Single Crystals for Enhanced Hard X-ray Detection.

Inorganic Bi-based perovskites have shown great potential in X-ray detection for their large absorption to X-rays, diverse low-dimensional structures, and eco-friendliness without toxic metals. However, they suffer from poor carrier transport properties compared to Pb-based perovskites. Here, we propose a mixed-halogen strategy to tune the structural dimensions and optoelectronic properties of Cs3 Bi2 I9-n Brn (0≤n≤9). Ten centimeter-sized single crystals are successfully grown by the Bridgman technique. Upon doping bromine to zero-dimensional Cs3 Bi2 I9 , the crystal transforms into a two-dimensional structure as the bromine content reaches Cs3 Bi2 I8 Br. Correspondingly, the optoelectronic properties are adjusted. Among these crystals, Cs3 Bi2 I8 Br exhibits negligible ion migration, moderate resistivity, and the best carrier transport capability. The sensitivities in 100 keV hard X-ray detection are 1.33×104 and 1.74×104 μC Gyair -1 cm-2 at room temperature and 75 °C, respectively, which are the highest among all reported bismuth perovskites. Moreover, the lowest detection limit of 28.6 nGyair s-1 and ultralow dark current drift of 9.12×10-9 nA cm-1 s-1 V-1 are obtained owing to the high ionic activation energy. Our work demonstrates that Br incorporation is an effective strategy to enhance the X-ray detection performance by tuning the dimensional and optoelectronic properties.

Dimensional and Optoelectronic Tuning of Lead‐free Perovskite Cs3Bi2I9−nBrn Single Crystals for Enhanced Hard X‐ray Detection

AbstractInorganic Bi‐based perovskites have shown great potential in X‐ray detection for their large absorption to X‐rays, diverse low‐dimensional structures, and eco‐friendliness without toxic metals. However, they suffer from poor carrier transport properties compared to Pb‐based perovskites. Here, we propose a mixed‐halogen strategy to tune the structural dimensions and optoelectronic properties of Cs3Bi2I9−nBrn (0≤n≤9). Ten centimeter‐sized single crystals are successfully grown by the Bridgman technique. Upon doping bromine to zero‐dimensional Cs3Bi2I9, the crystal transforms into a two‐dimensional structure as the bromine content reaches Cs3Bi2I8Br. Correspondingly, the optoelectronic properties are adjusted. Among these crystals, Cs3Bi2I8Br exhibits negligible ion migration, moderate resistivity, and the best carrier transport capability. The sensitivities in 100 keV hard X‐ray detection are 1.33×104 and 1.74×104 μC Gyair−1 cm−2 at room temperature and 75 °C, respectively, which are the highest among all reported bismuth perovskites. Moreover, the lowest detection limit of 28.6 nGyair s−1 and ultralow dark current drift of 9.12×10−9 nA cm−1 s−1 V−1 are obtained owing to the high ionic activation energy. Our work demonstrates that Br incorporation is an effective strategy to enhance the X‐ray detection performance by tuning the dimensional and optoelectronic properties.

Thermal and chemical durability of metal halide perovskite CsPbBr3 single crystals

Halide perovskite CsPbBr3 single crystals have shown promising applications in high-energy radiation detection because of their high gamma-ray blocking capability, strong hole carrier transport capability, and manufacturing feasibility. However, the soft ionic properties of perovskite octahedral lattice facilitate the phase transformation of CsPbBr3 under a hydrothermal environment, which significantly limits their application. The current work systematically studied the phase stability of the CsPbBr3 single crystals under high temperatures and high humidity to accelerate their potential application in high-energy radiation detection. Thermal and water degradation behaviors of the CsPbBr3 single crystals under elevated temperature were investigated for the first time via in situ Raman spectroscopy and semi-dynamic leaching testing methods. Results indicated that the CsPbBr3 single crystals exhibited good thermal stability below 460 °C without obvious phase degradation and rapidly transformed to CsPb2Br5, followed by PbBr(OH) with the continuous water interaction. The water interaction and phase degradation mechanism of single crystals with the preferential release of Cs, surface reorganization, and formation of PbBr(OH) alteration layer with rod-like structure was revealed. The phase degradation of CsPbBr3 single crystals along surface defects from the growth process was further confirmed, which can be used to guide subsequent work on single-crystal stability regulation.

Donor-Acceptor-Based Organic Polymer Semiconductor Materials to Achieve High Hole Mobility in Organic Field-Effect Transistors.

Organic polymer semiconductor materials are conveniently tuned to energy levels because of their good chemically modifiable properties, thus enhancing their carrier transport capabilities. Here, we have designed and prepared a polymer with a donor-acceptor structure and tested its potential as a p-type material for organic field-effect transistor (OFET) applications using a solution-processing method. The conjugated polymers, obtained via the polymerization of the two monomers relying on the Stille coupling reaction, possess extremely high molecular weights and thermodynamic stability. Theoretical-based calculations show that PDPP-2S-Se has superior planarity, which is favorable for carrier transport within the main chain. Photophysical and electrochemical measurements systematically investigated the properties of the material and the energy levels with respect to the theoretical values. The maximum hole mobility of the PDPP-2S-Se-based OFET device is 0.59 cm2 V-1 s-1, which makes it a useful material for potential organic electronics applications.

Perovskite-Based X-ray Detectors.

X-ray detection has widespread applications in medical diagnosis, non-destructive industrial radiography and safety inspection, and especially, medical diagnosis realized by medical X-ray detectors is presenting an increasing demand. Perovskite materials are excellent candidates for high-energy radiation detection based on their promising material properties such as excellent carrier transport capability and high effective atomic number. In this review paper, we introduce X-ray detectors using all kinds of halide perovskite materials along with various crystal structures and discuss their device performance in detail. Single-crystal perovskite was first fabricated as an active material for X-ray detectors, having excellent performance under X-ray illumination due to its superior photoelectric properties of X-ray attenuation with μm thickness. The X-ray detector based on inorganic perovskite shows good environmental stability and high X-ray sensitivity. Owing to anisotropic carrier transport capability, two-dimensional layered perovskites with a preferred orientation parallel to the substrate can effectively suppress the dark current of the device despite poor light response to X-rays, resulting in lower sensitivity for the device. Double perovskite applied for X-ray detectors shows better attenuation of X-rays due to the introduction of high-atomic-numbered elements. Additionally, its stable crystal structure can effectively lower the dark current of X-ray detectors. Environmentally friendly lead-free perovskite exhibits potential application in X-ray detectors by virtue of its high attenuation of X-rays. In the last section, we specifically introduce the up-scaling process technology for fabricating large-area and thick perovskite films for X-ray detectors, which is critical for the commercialization and mass production of perovskite-based X-ray detectors.