Electron-hole diffusion lengths \u3e175 μm in solution-grown CH\u3csub\u3e3\u3c/sub\u3eNH\u3csub\u3e3\u3c/sub\u3ePbI\u3csub\u3e3\u3c/sub\u3e single crystals

Long, balanced electron and hole diffusion lengths greater than 100 nanometers in polycrystalline CH3NH3PbI3 are critical for highly efficient perovskite solar cells. We report that the diffusion lengths in CH3NH3PbI3 single crystals grown by a solution-growth method can exceed 175 μm under 1 sun illumination and exceed 3 mm under weak light for both electrons and holes. The internal quantum efficiencies approach 100% in 3 mm-thick single crystal perovskite solar cells under weak light. These long diffusion lengths result from greater carrier mobility, lifetime and dramatically smaller trap densities in the single crystals than polycrystalline thin-films. The long carrier diffusion lengths enabled the use of CH3NH3PbI3 in radiation sensing and energy-harvesting through gammavoltaic effect with an efficiency of 3.9% measured with an intense cesium-137 source

An F82H steel pressurized tube creep capsule for irradiation in HFIR

A novel capsule design has been developed for measurement of irradiation creep in pressurized tubes and is being used to irradiate reduced activation ferritic/martensitic F82H steel creep test specimens. These tests are being conducted in the flux trap of the High Flux Isotope Reactor at the Oak Ridge National Laboratory. The capsule design uses a tight-fitting corrugated aluminum foil placed in the center of a vanadium alloy holder to conduct heat from the centrally located test specimen. The foil acts as a compressible thermal interface between the pressurized tube and holder, maintaining a constant thermal resistance (and thus a constant tube temperature gradient) during irradiation, regardless of differential thermal expansion, creep, and swelling in the test specimen. Mechanical interference with creep deformation of the specimen tube is minimized by using a thin (0.05 mm) foil with sufficient room to crush. Finite element analysis of the contact pressure between the specimen and foil, combined with thermal creep in the foil, showed little interference with specimen stress conditions. Specimens were designed to experience hoop stresses of 380, 300, 150, and 0 MPa at a temperature of 300 °C while being irradiated to a dose of 3.7 dpa. Passive SiC thermometry is located within the pressurized tube and the holder material for confirmation of experiment irradiation target temperatures. This work discusses aspects of the capsule's fabrication and design, including thermal models of the capsule during irradiation. Keywords: Pressurized tube, Irradiation creep, F82H IEA heat, HFI

An F82H steel pressurized tube creep capsule for irradiation in HFIR

A novel capsule design has been developed for measurement of irradiation creep in pressurized tubes and is being used to irradiate reduced activation ferritic/martensitic F82H steel creep test specimens. These tests are being conducted in the flux trap of the High Flux Isotope Reactor at the Oak Ridge National Laboratory. The capsule design uses a tight-fitting corrugated aluminum foil placed in the center of a vanadium alloy holder to conduct heat from the centrally located test specimen. The foil acts as a compressible thermal interface between the pressurized tube and holder, maintaining a constant thermal resistance (and thus a constant tube temperature gradient) during irradiation, regardless of differential thermal expansion, creep, and swelling in the test specimen. Mechanical interference with creep deformation of the specimen tube is minimized by using a thin (0.05 mm) foil with sufficient room to crush. Finite element analysis of the contact pressure between the spe-cimen and foil, combined with thermal creep in the foil, showed little interference with specimen stress conditions. Specimens were designed to experience hoop stresses of 380, 300, 150, and 0 MPa at a temperature of 300 °C while being irradiated to a dose of 3.7 dpa. Passive SiC thermometry is located within the pressurized tube and the holder material for confirmation of experiment irradiation target temperatures. This work discusses aspects of the capsule\u27s fabrication and design, including thermal models of the capsule during irradiation

Sensitive X-ray detectors made of methylammonium lead tribromide perovskite single crystals

The large mobilities and carrier lifetimes of hybrid perovskite single crystals and the high atomic numbers of Pb, I and Br make them ideal for X-ray and gamma-ray detection. Here, we report a sensitive X-ray detector made of methylammonium lead bromide perovskite single crystals. A record-high mobility-lifetime product of 1.2 x 10(-2) cm(2) V-1 and an extremely small surface charge recombination velocity of 64 cm s(-1) are realized by reducing the bulk defects and passivating surface traps. Single-crystal devices with a thickness of 2-3 mm show 16.4% detection efficiency at near zero bias under irradiation with continuum X-ray energy up to 50 keV. The lowest detectable X-ray dose rate is 0.5 mu Gy(air) s(-1) with a sensitivity of 80 mu C Gy(air)(-1) cm(-2), which is four times higher than the sensitivity achieved with alpha-Se X-ray detectors. This allows the radiation dose applied to a human body to be reduced for many medical and security check applications