Despite the impressive efficiency of perovskite solar cells (PSCs), their operational stability is still hindered by the thermodynamic instability of the hybrid organic–inorganic absorber layer with ABX₃ structure (A: organic/inorganic cation, B: metal cation, X: halogen anion and mixtures thereof). Due to the hygroscopic and volatile nature of the organic cations, i.e., methylammonium (MA⁺), they show very poor stability not only against thermal stress but also moisture. Therefore, a photoactive material free from organic components could offer great opportunities to prolong the operational stability of devices. In this context, all inorganic CsPbI_xBr_3−x perovskites are meticulously developed in terms of their structural/thermal stability and have triggered increasing research interest due to great prospects in the commercialization of perovskite technology. However, besides relatively low performance, the poor phase stability of inorganic perovskites associated with lattice strain and vacancies still requires a thorough understanding and permanent solutions for tackling these problems. In this comprehensive review, the recently reported B-site doping strategy in inorganic CsPbI_xBr_3−x perovskite thin films, which has been elucidated to passivate the defects, tune the grain orientation, and enhance the lifetime of charge-carriers, is presented based on different B-site elements belonging to group IIIA, IVA and VA, alkaline-earth, transition, and lanthanide metals. Solutions for confronting these current problems are elaborated and an outlook on further strategies is given.

Vanadium oxide (VO₂) is considered a Peierls–Mott insulator with a metal–insulator transition (MIT) at T_c = 68° C. The tuning of MIT parameters is a crucial point to use VO₂ within thermoelectric, electrochromic, or thermochromic applications. In this study, the effect of oxygen deficiencies, strain engineering, and metal tungsten doping are combined to tune the MIT with a low phase transition of 20 °C in the air without capsulation. Narrow hysteresis phase transition devices based on multilayer VO₂, WO₃, Mo_0.2W_0.8O_3, and/or MoO₃ oxide thin films deposited through a high vacuum sputtering are investigated. The deposited films are structurally, chemically, electrically, and optically characterized. Different conductivity behaviour was observed, with the highest value towards VO_1.75/WO_2.94 and the lowest VO_1.75 on FTO glass. VO_1.75/WO_2.94 showed a narrow hysteresis curve with a single-phase transition. Thanks to the role of oxygen vacancies, the MIT temperature decreased to 35 °C, while the lowest value (T_c = 20 °C) was reached with Mo_0.2W_0.8O₃/VO₂/MoO₃ structure. In this former sample, Mo_0.2W_0.8O₃ was used for the first time as an anti-reflective and anti-oxidative layer. The results showed that the MoO₃ bottom layer is more suitable than WO₃ to enhance the electrical properties of VO₂ thin films. This work is applied to fast phase transition devices.

Amorphous ZnWSe₂ alloy-based counter electrodes grown by magnetron sputtering technique can indeed possess superior optoelectronic properties, resulting in a substantial efficiency of 8.27% and prolonged photostability.

Dopant-free HTMs SP-09 and SP-10 are synthesized via a simple method. SP-10 enables 22.1% efficiency and superior stability in PSCs, outperforming spiro-OMeTAD, offering a cost-effective route toward efficient and durable perovskite devices.

This study was on the optoelectronic properties of multilayered two-dimensional MoS₂ and WS₂ materials on a silicon substrate using sputtering physical vapor deposition (PVD) and chemical vapor deposition (CVD) techniques. For the first time, we report ultraviolet (UV) photoresponses under air, CO₂, and O₂ environments at different flow rates. The electrical Hall effect measurement showed the existence of MoS₂ (n-type)/Si (p-type) and WS₂ (P-type)/Si (p-type) heterojunctions with a higher sheet carrier concentration of 5.50 × 10⁵ cm⁻² for WS₂ thin film. The IV electrical results revealed that WS₂ is more reactive than MoS₂ film under different gas stimuli. WS₂ film showed high stability under different bias voltages, even at zero bias voltage, due to the noticeably good carrier mobility of 29.8 × 10² cm²/V. WS₂ film indicated a fast rise/decay time of 0.23/0.21 s under air while a faster response of 0.190/0.10 s under a CO₂ environment was observed. Additionally, the external quantum efficiency of WS₂ revealed a remarkable enhancement in the CO₂ environment of 1.62 × 10⁸ compared to MoS₂ film with 6.74 × 10⁶. According to our findings, the presence of CO₂ on the surface of WS₂ improves such optoelectronic properties as photocurrent gain, photoresponsivity, external quantum efficiency, and detectivity. These results indicate potential applications of WS₂ as a photodetector under gas stimuli for future optoelectronic applications.