Abstract In the past 10 years, ZnO as a semiconductor has attracted considerable attention due to its unique properties, such as high electron mobility, wide and direct band gap and large exciton binding energy. ZnO has been considered a promising material for optoelectronic device applications, and the fabrications of high quality p-type ZnO and p–n junction are the key steps to realize these applications. However, the reliable p-type doping of the material remains a major challenge because of the self-compensation from native donor defects (V O and Zn i ) and/or hydrogen incorporation. Considerable efforts have been made to obtain p-type ZnO by doping different elements with various techniques. Remarkable progresses have been achieved, both theoretically and experimentally. In this paper, we discuss p-type ZnO materials: theory, growth, properties and devices, comprehensively. We first discuss the native defects in ZnO. Among the native defects in ZnO, V Zn and O i act as acceptors. We then present the theory of p-type doping in ZnO, and summarize the growth techniques for p-type ZnO and the properties of p-type ZnO materials. Theoretically, the principles of selection of p-type dopant, codoping method and X Zn –2V Zn acceptor model are introduced. Experimentally, besides the intrinsic p-type ZnO grown at O-rich ambient, p-type ZnO (MgZnO) materials have been prepared by various techniques using Group-I, IV and V elements. We pay a special attention to the band gap of p-type ZnO by band-gap engineering and room temperature ferromagnetism observed in p-type ZnO. Finally, we summarize the devices based on p-type ZnO materials.

RaoP-Type ZnO Materials: Theory, Growth, Properties, and Devices

Resveratrol for breast cancer prevention and therapy: Preclinical evidence and molecular mechanisms.

Recently the developments in the field of II-VI-oxides have been spectacular. Various epitaxial methods has been used to grow epitaxial ZnO layers. Not only epilayers but also sufficiently good-quality multiple quantum wells (MQWs) have also been grown by laser molecular-beam epitaxy (laser-MBE). We discuss mainly the experimental aspect of the optical properties of excitons in ZnO-based MQW heterostructures. Systematic temperature-dependent studies of optical absorption and photoluminescence in these MQWs were used to evaluate the well-width dependence and the composition dependence of the major excitonic properties. Based on these data, the localization of excitons, the influence of exciton-phonon interaction, and quantum-confined Stark effects are discussed. 
The optical spectra of dense excitonic systems are shown to be determined mainly by the interaction process between excitons and biexcitons. The high-density excitonic effects play a role for the observation of room-temperature stimulated emission in the ZnO MQWs. The binding energies of exciton and biexciton are enhanced from the bulk values, as a result of quantum-confinement effects.

Optical Properties of Excitons in ZnO-based Quantum Well Heterostructures

Surface plasmon resonance (SPR) has been intensively studied and widely employed for light trapping and absorption enhancement. In the mid-infrared and terahertz (THz) regime, graphene supports the tunable SPR via manipulating its Fermi energy and enhances light-matter interaction at the selective wavelength. In this work, periodic arrays of graphene rings are proposed to introduce tunable light trapping with good angle polarization tolerance and enhance the absorption in the light-absorbing materials nearby to more than one order. Moreover, the design principle here could be set as a template to achieve multi-band plasmonic absorption enhancement by introducing more graphene concentric rings into each unit cell. This work not only opens up new ways of employing graphene SPR, but also leads to practical applications in high-performance simultaneous multi-color photodetection with high efficiency and tunable spectral selectivity.

Tunable light trapping and absorption enhancement with graphene ring arrays

Surface plasmon resonance (SPR) has been intensively studied and widely employed for light trapping and absorption enhancement. In the mid-infrared and terahertz (THz) regime, graphene supports tunable SPR via manipulating its Fermi energy and enhances light–matter interaction at the selected wavelength. Most previous studies have concentrated on the absorption enhancement in graphene itself while little attention has been paid to trapping light and enhancing the light absorption in other light-absorbing materials with graphene SPR. In this work, periodic arrays of graphene rings are proposed to introduce tunable light trapping with good angle polarization tolerance and enhance the absorption in the surrounding light-absorbing materials by more than one order of magnitude. Moreover, the design principle here could be set as a template to achieve multi-band plasmonic absorption enhancement by introducing more graphene concentric rings into each unit cell. This work not only opens up new ways of employing graphene SPR, but also leads to practical applications in high-performance simultaneous multi-color photodetection with high efficiency and tunable spectral selectivity.

Comparative Studies of Powder Flow Predictions Using Milligrams of Powder for Identifying Powder Flow Issues.

The proposed lead-free Cs3Sb2Br9 (Cesium Antimony Bromide) perovskite is newly discovered material with numerous beneficial optoelectronics properties and nontoxic. While this proposed perovskite used in optoelectronics applications before. For the first time, we proposed Cs3Sb2Br9 as an absorber within a solar cell device. With its optimized parameters, our proposed perovskite solar cell (PSC) achieved an impressive power conversion efficiency (PCE) of 12.88% having open-circuit voltage (VOC) of 2.07 V, short-circuit current density (JSC) of 7.01 mA/cm2, and fill factor (FF) of 88.63% which is considerable performance of Cs3Sb2Br9 PSC in comparison to other reported Cs based PSCs in the study.

A model development of lead-free Cs 3 Sb 2 Br 9 based novel perovskite solar cell by SCAPS-1D

A Review on Sputtered Chalcopyrite and Kesterite Thin Film Solar Cell

Purpose: The association between exposure to Toxocara canis and epilepsy is at the best contentious. Most of previous studies were retrospective, community-based, and contradictory to one another. As the impact of a positive association on the magnitude of epilepsy will be huge especially in developing countries where toxocariasis is common owing to poor hygienic practices, this study was carried out to determine whether exposure to T. canis predisposes to development of epilepsy. Patients and Methods: This case-controlled observational study was carried out a tertiary healthcare center in North India on 120 patients with newly diagnosed epilepsy who presented within 3 months of diagnosis. A total of 120 age- and sex-matched individuals from the same community were chosen as controls. Epilepsy was defined according to ILAE 1993 definition. Serological testing for T. canis was carried out using commercially available ELISA kits. All the positive samples were subjected to Western blot testing for confirmation. Results: The prevalence of antibodies to T. canis was similar in cases (16/120; 13.3%) and controls (16/120; 13.3%). Among the various risk factors, history of pica was significantly associated with T. canis seropositivity, while lack of hand washing was significantly associated with higher risk of epilepsy. Conclusion: Our study could not find any association between exposure to T. canis and epilepsy.

Exposure to Toxocara Canis is not Associated with New-Onset Epilepsy

Electrical and optical properties of dual ion-beam sputtered (DIBS) Ga-doped ZnO (GZO) and Ga-doped MgZnO (GMZO) individual films are analyzed. Usage of secondary ion source favors excitation of sputter-instigated plasmonic feature in individual thin film. The plasmonic feature observed in GZO and GMZO thin films due to the formation of metal and metal oxide nanoclusters. The plasmon generation is verified by electron energy loss spectra obtained by ultraviolet photoelectron spectroscopy, spectroscopic Ellipsometry, and field emission scanning-electron microscopy measurements. This is promising in terms of increasing the efficiency of ultrathin solar cells by increasing optical path length in the absorbing layer.

Vivek Garg

Papers

Comparative Studies of Powder Flow Predictions Using Milligrams of Powder for Identifying Powder Flow Issues.

A model development of lead-free Cs 3 Sb 2 Br 9 based novel perovskite solar cell by SCAPS-1D

A Review on Sputtered Chalcopyrite and Kesterite Thin Film Solar Cell

Exposure to Toxocara Canis is not Associated with New-Onset Epilepsy

Dual ion beam sputtered TCO thin films: Sputter-instigated plasmonic features for ultrathin photovoltaics