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.