Perovskite-based semiconductors, such as methylammonium and cesium lead halides (MPbX3: M = CH3NH3 + or Cs+; X = I–, Br–, or Cl–), have attracted immense attention for several applications, including radiation detection, due to their excellent electronic and optical properties.1,2,3,4,5,6 In addition, the combination of perovskites with other materials enables unique device structures. For example, robust and reliable diodes result when combined with metal oxide semiconductors. This device can be used for detection of nonionizing and ionizing radiation. In this paper, we report a unique perovskite single-crystal-based neutron detector using a heterojunction diode based on single-crystal MAPbBr3 and gallium oxide (Ga2O3) thin film. The MAPbBr3/Ga2O3 diodes demonstrate a leakage current of ∼7 × 10–10 A/mm2, an on/off ratio of ∼102, an ideality factor of 1.41, and minimal hysteresis that enables alpha particle, gamma-ray, and neutron detection at a bias as low as (−5 V). Gamma discrimination is further improved by 85% by optimizing the thickness of the perovskite single crystal. The MAPbBr3/Ga2O3 diodes also demonstrate a neutron detection efficiency of ∼3.92% when combined with a 10B neutron conversion layer.

A small cross-section of silver nanoparticles (AgNPs) placed at the rear-part of the solar cell avoids the parasitic absorption of the nanoparticles which is the biggest barrier for plasmonic structures when acting as photocurrent enhancers. Herein, we demonstrate p-i-n planar perovskite solar cells with the structure ITO/PEDOT:PSS/MAPbI3/PCBM/Ni:Au, where the PCBM electron extraction layer (EEL) was intentionally modified with variable amounts of AgNPs. The addition of small amounts of AgNPs (e.g., 5 wt. %) into the PCBM improved the overall reproducibility and reliability of the solar cell fabrication process after optimization. Plasmonic simulations suggest that any plasmonic-optical effects are relatively small compared to sample absorbance due to perovskite alone. It has been concluded that plasmonic-electrical effects play a major role in averaged performance improvement. Therefore, the addition of small AgNPs in low concentration to the EEL layer accounts for higher Jsc, Voc and FF as a result of a better perovskite coverage by the EEL and an improved charge carrier collection as evidenced by morphological and electrical analysis.

Two‐dimensional materials such as graphene and MoS2 have been the main focus of intense research efforts over the past few years. The most common method of exfoliating these materials, although efficient for lab‐scale experiments, is not acceptable for large area and practical applications. Here, we report the deposition of MoS2 layered films on amorphous (SiO2) and crystalline substrates (sapphire) using a pulsed laser deposition (PLD) method. Increased substrate temperature (∼700 °C) and laser energy density (>530 mJ /cm2) promotes crystalline MoS2 films < 20 nm, as demonstrated by fast Fourier transform (FFT) and transmission electron microscopy (TEM). The method reported here opens the possibility for large area layered MoS2 films by using a laser ablation processes. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

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Hybrid organic-inorganic lead halide perovskite materials show great promise in a number of optoelectronic applications, including solar cells, light emitting diodes, and photodetectors. Understanding their intrinsic material properties is critical to enhancing device performance and enabling innovative material and device designs. Here, we study lattice dynamics using far-infrared (FIR) reflectance and photogenerated carrier dynamics using surface photovoltage (SPV) measurements on high-quality methylammonium lead bromide (MAPbBr3) single crystals. FIR reflectance shows three coherent infrared-active phonon modes between 40 and 200 cm−1 that result in reststrahlen bands with much higher peak reflectance than has been previously reported. The phonon mode strength and damping are comparable to classical oxide perovskite single crystals. However, the effects of defects on photogenerated carrier recombination are still evident in SPV measurements. By performing SPV over different spectral ranges, we are able to separate the effects of surface and bulk defects on the recombination dynamics of photogenerated charge carriers. We further apply SPV measurements to obtain the minority carrier (electron) diffusion length for the MAPbBr3 crystal. This study demonstrates that both FIR reflectance and SPV measurements provide useful information on the electromagnetic response properties of halide perovskite single crystals.

The optimization of interrelated deposition parameters during deposition of in situ YBa2Cu3O7 thin films on MgO 〈001〉 substrates by KrF laser ablation was systematically studied in a single experimental chamber. The optimum condition was found to be a substrate temperature of 720 °C and a target-substrate distance of 5 cm in an oxygen partial pressure of 100 mTorr. These conditions produced films with Tc = 87 K. The presence of YO in the plasma plume was found to be important in producing good quality films. The films were characterized by resistance-temperature measurements, energy dispersive x-ray analyses, scanning electron microscopy, and x-ray-diffraction measurements, and the physical reasons underlying film quality degradation at parameter values away from optimal are discussed.

Zinc oxide (ZnO) films are deposited onto glass, silicon oxide, and hafnium oxide substrates via the successive ionic layer adsorption and reaction (SILAR) method. The substrates are subjected to an oxygen plasma treatment prior to the deposition to increase the hydrophilic character of the film surface and improve the morphological and structural properties of the resulting ZnO films. Crystallinity, surface morphology, and thickness of the films with and without the plasma treatment are thoroughly evaluated by multiple characterization techniques. The oxygen plasma treatment increases the substrate's surface roughness significantly which results in an increase in the nucleation sites. The plasma treatment yields thicker films in all the substrates compared with substrates without the plasma treatment. The thickness of the ZnO deposited on glass substrates increases as the rinsing time increases, while the opposite is observed for films deposited on both silicon and hafnium oxide substrates. The higher porosity of the ZnO films grown on silicon dioxide and hafnium dioxide substrates leads to a higher surface area that increases the removal of the deposited ZnO on these substrates with the rinsing during the SILAR deposition, resulting in an overall thickness reduction of the film.