Xu-Dong Wang

In melamine cation-based perovskitoid single crystals, the distinct Bi ³⁺ and Pb ²⁺ synergistically modulate network topology. The Bi-based photodetector achieves an on/off ratio 15 times higher than that of its Pb-based counterpart.

Halide perovskite thick films have emerged as promising candidates for X‐ray detection and imaging. However, the residual strain arising from soft lattice, lattice mismatch, and weak interfacial bonding causes cracks and delamination, hindering the integration of perovskite film with thin film transistor (TFT). Here, a multifunctional natural molecule (digallic acid, DA) is introduced into the ultrasonic spraying perovskite film to achieve efficient and stable fully air‐processed X‐ray detectors. Results demonstrate that DA's abundant functional groups not only enhance adhesion between perovskite films and substrates to improve the integrability with TFT, but also effectively passivate defects. Furthermore, this approach modulates the perovskite's Fermi level, creating an interfacial barrier that significantly reduces dark current. Consequently, DA modification enables the device to obtain a high sensitivity of 3.1 × 10 ⁵ µC Gy _air ⁻¹ cm ⁻² and a low detection limit of 39.8 nGy _air s ⁻¹ , simultaneously greatly enhances the tolerance to irradiation, remaining stable after 140 Gy _air X‐ray irradiation. The flat‐panel detector, integrating DA‐modified perovskite film with TFT backplane, successfully achieved rapid X‐ray imaging under low dose rate (92 ms/frame, 27.2 µGy _air s ⁻¹ , tolal dose of 2.5 µGy _air ). This work highlights DA's potential as a versatile molecular tool for developing low‐dose, high‐performance X‐ray imaging systems.

Formamidinium lead iodide (FAPbI₃) perovskite exhibits an impressive X-ray absorption coefficient and a large carrier mobility-lifetime product (µτ), making it as a highly promising candidate for X-ray detection application. However, the presence of larger FA⁺ cation induces to an expansion of the Pb-I octahedral framework, which unfortunately affects both the stability and charge carrier mobility of the corresponding devices. To address this challenge, we develop a novel low-dimensional (HtrzT)PbI₃ perovskite featuring a conjugated organic cation (1H-1,2,4-Triazole-3-thiol, HtrzT⁺) which matches well with the α-FAPbI₃ lattices in two-dimensional plane. Benefiting from the matched lattice between (HtrzT)PbI₃ and α-FAPbI₃, the anchored lattice enhances the Pb-I bond strength and effectively mitigates the inherent tensile strain of the α-FAPbI₃ crystal lattice. The X-ray detector based on (HtrzT)PbI₃(1.0)/FAPbI₃ device achieves a remarkable sensitivity up to 1.83 × 10⁵ μC Gy_air ⁻¹ cm⁻², along with a low detection limit of 27.6 nGy_air s⁻¹, attributed to the release of residual stress, and the enhancement in carrier mobility-lifetime product. Furthermore, the detector exhibits outstanding stability under X-ray irradiation with tolerating doses equivalent to nearly 1.17 × 10⁶ chest imaging doses.

Large‐area perovskite (PVK) X‐ray detectors exhibit significant potential for commercial applications. However, the production of uniform and dense thick films as well as achieving efficient carrier transport over tens of microns in thick PVK films, remain major challenges for highly sensitive X‐ray detection. Herein, an innovative vacuum‐assisted blade coating strategy is proposed using PVK inks that strictly controls the nucleation and growth of PVKs to prepare large‐area, high‐quality MAPbI ₃ homojunction thick films. Arising from the formation of a type II homojunction between the top and bottom PVK layers, and effective reduction of the density of defect states, the resultant homojunction film exhibits impressive performances, including an increase in carrier lifetime from 1272 to 9335 ps, an increase in surface photovoltage change from 93 to 386 mV, and nearly three times higher carrier mobility‐lifetime product compared with pristine NMP‐PVK film. Consequently, the X‐ray detector based on homojunction film demonstrates a high sensitivity of 1.3 × 10 ⁵ µC Gy _air ⁻¹ cm ⁻² , surpassing the most previously reported values for X‐ray detector using blade coating method. This research provides a convenient approach for preparing large‐area PVK thick films and establishes a solid foundation for the development of X‐ray detection.

Bi-based halide perovskites, with much lower toxicity than Pb-based perovskites, have triggered enormous interest in optoelectronic applications. However, most Bi-based perovskites have low-dimensional crystalline structures which may have potential negative effects on carrier transport. Herein, zero-dimensional (CHDA)BiI₅·3H₂O is transformed into two-dimensional double perovskite (CHDA)₂CuBiI₈·0.5H₂O through Cu⁺ introduction engineering, which shows increased orbital overlap and improved electronic band structure dispersion compared with the former. Notably, a 104-fold enhancement in photoresponse on–off ratio is observed for the (CHDA)₂CuBiI₈·0.5H₂O SC photodetector. This advancement not only enhances our understanding of the intricate relationship between crystal structure and charge transport behavior in Bi-based perovskites but also paves the way for highly efficient and environmentally friendly optoelectronic device development.

Hybrid organic–inorganic lead halide perovskite single crystal thin film (SCTF) recently has attracted enormous interest in the field of optoelectronic devices, since it efficiently resolves the trade‐off between thickness and carrier diffusion length. However, the toxicity of lead element and the instability induced by organic component still hinder its future developments. In this work, lead‐free all‐inorganic Cs₃Bi₂I₉ SCTF with a high orientation along (00h) has been in situ grown on indium tin oxide (ITO) glass via a space‐limited solvent evaporation crystallization method. The trap density of Cs₃Bi₂I₉ SCTF (5.7 × 10¹² cm⁻³) is 263 folds lower than that of the polycrystalline thin film (PCTF) counterpart, together with a 5‐order‐of‐magnitude higher carrier mobility. These superior charge transfer properties enable a photoresponse on–off ratio as high as 11 000, which far surpasses that of the PCTF device by 460 folds, comparable to the lead halide perovskite. Furthermore, the Cs₃Bi₂I₉ SCTF photodetector exhibits outstanding stability even without any encapsulation, whose initial performance is well maintained after aging 1000 h in humid air of 50% RH or continuous on–off light illumination for 20 h. This work will pave the way to produce new families of high‐performance, stable, and nontoxic perovskite SCTF for future optoelectronic applications.

Cupric oxide (CuO), a narrow-bandgap semiconductor, has a band alignment that makes it an ideal photocathode for the renewable production of solar fuels. However, the photoelectrochemical performance of CuO is limited by its poor conductivity and short electron diffusion lengths. Herein, a three-dimensional (3D) architecture consisting of CuO nanosheets supported onto transparent conducting macroporous antimony-doped tin oxide (mpATO@CuONSs) is designed as an excellent photocathode for promoting the hydrogen evolution reaction (HER). Owing to the 3D structure affording superior light-harvesting characteristics, large contact areas with the electrolyte, and highly conductive pathways for separation and transport of charge carriers, the mpATO@CuONSs photocathode produces an impressively high photocurrent density of −4.6 mA cm⁻² at 0 V versus the reversible hydrogen electrode (RHE), which is much higher than that of the CuONSs array onto planar FTO glass (−1.9 mA cm⁻²).