p-type Bi0.4Sb1.6Te3 nanocomposites with enhanced figure of merit

Ion migration in halide perovskite materials usually brings an intractable problem in the working stability of solar cells and photoelectrical detectors. The mechanism of ion migration and its impact on physical properties are still open questions. In this work, the ion migration behavior in solution-grown CsPbBr3 crystals was observed by the hysteresis in current–voltage curves and the temperature dependent reversed current–time measurements. Defect proliferation phenomena (new defects of [VCs]− and [PbBr]2+) originating from ion migration were verified by thermally stimulated current spectroscopy. Our results also give evidence that Cs+ ions also participate in the process of ion migration except the widely considered Br− ions. Furthermore, the photoelectric properties of the CsPbBr3 device were found to be seriously deteriorated after the ion migration. Our work demonstrates the strong correlation between the ion migration and physical properties in halide perovskites.

Normal flat panel X-ray detectors are confined in imaging of curved surfaces and three-dimensional objects. Except that, their rigid panels provide uncomfortable user experience in medical diagnosis. Here, we report a flexible X-ray detector fabricated by the combination of a lead-free Cs2TeI6 perovskite film and a polyimide (PI) substrate. High-quality Cs2TeI6 polycrystalline films are prepared by a low-temperature electrospraying method. The resistivity even remained at the level of 1011 Ω·cm after 100 cycles of bending tests with a low bending radius of 10 mm. The resulting flexible Cs2TeI6 detectors exhibit better response stability than those based on rigid SnO2:F glass (FTO), which is attributed to the superior crystallization of films and the growth stress relief of flexible substrates. Furthermore, an X-ray sensitivity of 76.27 μC·Gyair –1·cm–2 and a detection limit of 0.17 μGyair·s–1 are achieved. A series of distortion-free clear X-ray images are obtained for objects with different materials and densities. These findings provide insights into flexible X-ray detectors based on perovskite films and motivate research in wearable X-ray detectors for medical radiography and dose monitoring.

Effective governance of thermal conductivity and other properties is of significant interest for science, including the fields of thermal barrier coatings, thermoelectric materials, and limit alloys. In this study, we investigated the impact of entropy engineering on properties of fluorite RE3NbO7, and limit thermal conductivity and strengthened mechanical properties are achieved. The solution strengthening mechanism leads to an 80% increase in toughness when the intrinsic stiffness and Young's modulus of the fabricated samples are identified via nanoindentation. Thermal conductivity is as low as 1.03–1.17 W m−1 K−1 at 25–900 °C, drastically reducing the gap between experimental results and theoretical limit values of fluorite RE3NbO7. The limit thermal conductivity as well as enhanced thermal expansion coefficients (11.2 × 10−6 K−1) and mechanical properties imply that the working performance of RE3NbO7 is evidently promoted by entropy engineering.

Halide perovskite semiconductors exhibit ultralow thermal conductivities, making them potentially suitable for thermoelectric applications. Nevertheless, the thermoelectric properties of the prototypical halide perovskite of CH 3 NH 3 PbI 3 have been limited with a very low dimensionless figure of merit (ZT) and a narrow operating temperature window, which are attributed to its poor electronic conductivity and unstable hybrid organic−inorganic composition, respectively. Here, we report the bulk synthesis of a stable, all-inorganic halide perovskite of CsSn 0.8 Ge 0.2 I 3 as a new thermoelectric material, which shows a 10 order of magnitude enhancement in ZT compared with that of CH 3 NH 3 PbI 3 and an operating temperature as high as 473 K. Importantly, this CsSn 0.8 Ge 0.2 I 3 perovskite is also Pb-free in the composition, attesting its high potential as an environmentally friendly candidate material for future thermoelectrics.