This article presents a strategic review of secondary phases, defects and defect-complexes in kesterite CZTS–Se solar cells responsible for performance gap from CIGS solar cells.

With the use of UV‐C radiation sterilizers on the rise in the wake of the recent pandemic, it has become imperative to have health safety systems in place to curb the ill‐effects on humans. This requires detection systems with suitable spectral response to the “invisible to the naked eye” radiation leaks with utmost sensitivity and swiftness. State of the art deep‐UV photodetectors based on the wide bandgap material gallium oxide have achieved responsivities up to few hundred A W−1 while the minimum response time achieved is few hundred nanoseconds. However, due to the trade‐off between these two key parameters, the ultimate performance of the photodetectors remains inadequate. The focus here is to give a thorough review of the gallium oxide based photodetectors, their recent progress and future prospects. This review highlights the fundamental physics and the key parameters such as dark current, responsivity, and response time with their dependence on the material properties. Exploration of the reasons behind current scenario in the field of gallium oxide is comprehensively and critically analyzed. The key challenges which limit device performance and inhibit the realization of real‐world practical detectors are also described. The lacunae currently plaguing the field is also discussed with possible remedial solutions.

The article presents a strategic review of secondary phases, defects and defect-complexes in kesterite CZTSSe solar cells responsible for performance gap compared to CIGS solar cells.

Toxic gases are produced during the burning of fossil fuels. Room temperature (RT) fast detection of toxic gases is still challenging. Recently, MoS transition metal dichalcogenides have sparked great attention in the research community due to their performance in gas sensing applications. However, MoS based gas sensors still suffer from long response and recovery times, especially at RT. Considering this challenge, here, we report photoactivated highly reversible and fast detection of NO sensors at room temperature (RT) by using mixed in-plane and edge-enriched p-MoS flakes (mixed MoS). The sensor showed fast response with good sensitivity of ∼10.36% for 10 ppm of NO at RT without complete recovery. However, complete recovery was obtained with better sensor performance under UV light illumination at RT. The UV assisted NO sensing showed improved performance in terms of fast response and recovery kinetics with enhanced sensitivity to 10 ppm NO concentration. The sensor performance is also investigated under thermal energy, and a better sensor performance with reduced sensitivity and high selectivity toward NO was observed. A detailed gas sensing mechanism based on the density functional theory (DFT) calculations for favorable NO adsorption sites on in-plane and edge-enriched MoS flakes is proposed. This study revealed the role of favorable adsorption sites in MoS flakes for the enhanced interaction of target gases and developed a highly sensitive, reversible, and fast gas sensor for next-generation toxic gases at room temperature.

A sixfold decrease in photoluminescence signal intensity at 590nm with increase in deposition time from 3to12h has been observed in single crystalline indium oxide octahedron structures grown by vapor-phase evaporation method. Electron paramagnetic resonance and energy dispersive x-ray analysis confirm that the concentration of oxygen vacancies increases with deposition time. These results are contrary to the previous reports where oxygen vacancies were shown to be responsible for photoluminescence in indium oxide structures. Our results indicate that indium interstitials and their associated complex defects other than oxygen vacancies are responsible for the photoluminescence in In2O3 microstructures.

Fabrication of heterojunction between 2D molybdenum disulfide (MoS2) and gallium nitride (GaN) and its photodetection properties have been reported in the present work. Surface potential mapping at the MoS2/GaN heterojunction is done using Kelvin Probe Force Microscopy to measure the conduction band offset. Current-voltage measurements show a diode like behavior of the heterojunction. The origin of diode like behavior is attributed to unique type II band alignment of the heterojunction. The photocurrent, photoresponsivity and detectivity of the heterojunction are found to be dependent on power density of the light. Photoresponse investigations reveal that the heterojunction is highly sensitive to 405 nm laser with very high responsivity up to 105 A/W. The heterojunction also shows very high detectivity of the order of 1014 Jones. Moreover, the device shows photoresponse in UV region also. These observations suggest that MoS2/GaN heterojunction can have great potential for photodetection applications.

CZTSSe solar cells are considered to be potential and cost-effective alternative solution to matured photovoltaic technology to meet future energy demands. However, the current performance of CZTSSe solar cells is...

Nitrogen dioxide (NO2), a hazardous gas with acidic nature, is continuously being liberated in the atmosphere due to human activity. The NO2 sensors based on traditional materials have limitations of high-temperature requirements, slow recovery, and performance degradation under harsh environmental conditions. These limitations of traditional materials are forcing the scientific community to discover future alternative NO2 sensitive materials. Molybdenum disulfide (MoS2) has emerged as a potential candidate for developing next-generation NO2 gas sensors. MoS2 has a large surface area for NO2 molecules adsorption with controllable morphologies, facile integration with other materials and compatibility with internet of things (IoT) devices. The aim of this review is to provide a detailed overview of the fabrication of MoS2 chemiresistance sensors in terms of devices (resistor and transistor), layer thickness, morphology control, defect tailoring, heterostructure, metal nanoparticle doping, and through light illumination. Moreover, the experimental and theoretical aspects used in designing MoS2-based NO2 sensors are also discussed extensively. Finally, the review concludes the challenges and future perspectives to further enhance the gas-sensing performance of MoS2. Understanding and addressing these issues are expected to yield the development of highly reliable and industry standard chemiresistance NO2 gas sensors for environmental monitoring.