Sintered Polycrystalline BiVO4 Pellet for Stable X-Ray Detector with Low Detection Limit

Semiconductors based on Bi element show large attenuation coefficients to X-ray photons and have been recognized as candidates for X-ray detectors. However, the application of stable Bi-based oxide materials to X-ray detectors has been rarely investigated. In this research, the X-ray response of a BiVO₄ pellet has been studied. It has been found that the BiVO₄ pellet has a large resistivity of 1.3 × 10¹² Ω cm, negligible current drift of 6.18 × 10⁻⁸ nA cm⁻¹ s⁻¹ V⁻¹ under electrical bias and mobility lifetime product, µτ, of 1.75 × 10⁻⁴ cm² V⁻¹, which renders the pellet with an X-ray sensitivity of 241.3 µC Gy_air⁻¹ cm⁻² and a detection limit of 62 nGy_air s⁻¹ under 40 KVp X-ray illumination and 40 V bias voltage. The BiVO₄ pellet also shows operational stability under steady X-ray illumination with total dose of 2.01 Gy_air, equal to the dose of 20 000 medical chest X-ray inspections. This research reveals the potential application of BiVO₄ in X-ray detection devices and inspires further research in this area.     

Highly-Stable CsPbI3 Perovskite Solar Cells with an Efficiency of 21.11% via Fluorinated 4-Amino-Benzoate Cesium Bifacial Passivation

The poor interface quality between cesium lead triiodide (CsPbI₃) perovskite and the electron transport layer limits the stability and efficiency of CsPbI₃ perovskite solar cells (PSCs). Herein, a 4-amino-2,3,5,6-tetrafluorobenzoate cesium (ATFC) is designed as a bifacial defect passivator to tailor the perovskite/TiO₂ interface. The comprehensive experiments demonstrate that ATFC can not only optimize the conductivity, electron mobility, and energy band structure of the TiO₂ layer by passivation of the undercoordinated Ti⁴⁺, oxygen vacancy (V_O), and free  OH defects but also promote the yield of high-quality CsPbI₃ film by synergistic passivation of undercoordinated Pb²⁺ defects with the  CO group and F atom, and limiting I⁻ migration via F···I interaction. Benefiting from the above interactions, the ATFC-modified CsPbI₃ device yields a champion power conversion efficiency (PCE) of 21.11% and an excellent open-circuit voltage (V_OC) of 1.24 V. Meanwhile, the optimized CsPbI₃ PSC maintains 92.74% of its initial efficiency after aging 800 h in air atmosphere, and has almost no efficiency attenuation after tracking at maximum power point for 350 h.     

Composition Engineering of Perovskite Single Crystals for High-Performance Optoelectronics

Composition engineering, with its advantages to effectively tune semiconductor properties by regulating chemical stoichiometry, is a proven strategy to boost the efficiency and stability of ABX₃ perovskite photoelectronic devices. Compared with its counterpart polycrystalline perovskite film, single crystalline is the ideal model for exploring its fundamental scientific issues. In this review, a critical overview of recent advances of the growth strategies, properties, and functional applications of multicomponent perovskite single crystals (SCs) is presented. First, the underlying advantages of composition engineering of perovskite SCs are discussed and then the different composition tuning strategies, including A-site, B-site, X-site, and simultaneous A- and X-site engineering, are systematically summarized. Subsequently, the benefits of composition engineering are highlighted for optimizing photovoltaic and photoelectronic devices. Lastly, controversies and remaining challenges for the development of composition engineering of perovskite SCs are discussed and a brief perspective regarding further investigation in this field is provided.