technologies based on crystalline silicon, cadmium telluride (CdTe), copper indium gallium selenide (CIGS), etc. [15,16] Tremendous efforts are being given to commercialization of PSCs through improving the device efficiency, stability, and ability to fabricate large-area perovskite films. Though the current efficiency of PSCs is comparable to other matured solar cell technologies, this technology is behind those in terms of stability and large-area fabrication ability. Hopefully, various technologies have come out as potential largearea film fabrication methods, like blade coating, spray coating, slot-die coating, roll printing, etc. [17-20] Furthermore, stability can be improved mostly by encapsulation technologies and using additives in precursor solutions, but still not up to the mark for commercial use, which leaves a huge space for further research. [15,21-24] At the beginning of the perovskite solar cell era, uniform and pinhole-free perovskite film formation was a challenge. It is notable that, pinholes lead to a decrease in shunt resistance and nonuniformity leads to an increase in series resistance, which ultimately produce poor efficiency and stability of the device. Gradually, various technologies had been developed to improve the overall film quality, i.e., to obtain uniform and fully covered films. Among those technologies, the use of antisolvents during the perovskite film formation became very successful to obtain uniform and pinhole-free film, which dramatically increased the efficiency of the devices (also improved the stability to some extent). Antisolvents induce rapid and dense nucleation of perovskite that lead to uniform and pinhole free films. [25] Other effective alternative technologies are additive engineering, [26] hot casting, [27] rapid thermal annealing, [28] and solvent annealing. [29,30] In additive engineering, additives are used generally to slow down the crystallization process of perovskite or defect passivation to improve the crystallinity and optoelectronic properties of the perovskite film. In hot casting, hot precursor solution is coated on a hot substrate for better crystallization that improves the perovskite film quality. In rapid thermal annealing, a high intensity radiation is applied for post-annealing of perovskite film. In solvent annealing, a solvent vapor is allowed to condense on the surface, voids, and grain boundaries of the film, in which the perovskite dissolve and recrystallize to reduce the grain boundaries and pinholes. Interestingly, the best efficiency solar cells are mostly fabricated by using antisolvents. Therefore, a review article on the use of Organic-inorganic metal halide perovskite solar cells are emerging as potential solar energy harvesting tools and can be a tough competitor to already matured solar cell technologies. The success of perovskite solar cells is attributed to superior optoelectronic properties of perovskites, feasible synthesis process, and low fabrication cost. Though perovskite solar cells confront perovskite film quality rela...

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The perovskite solar cells (PSCs) have emerged as an established technology during the last decade, with the record efficiency of such solar cells having increased from 3.8 % to 25.5 %. Recently, flexible perovskite solar cells (fPSCs) have received much attention from the academic and the industrial communities, owing to their potential for various niche applications, including portable electronics, wearable power sources, electronic textiles, and large‐scale industrial roofing. fPSCs are lightweight, bendable, and suitable for roll‐to‐roll industrial production and can be integrated easily over any surface. This Review discusses the recent development of materials for fPSCs based on various flexible substrates, including plastic, metal, and other flexible substrates, as well as fiber‐shaped perovskite solar cells, with a focus on the device structure, material selection for each layer, mechanical flexibility and the environmental stability of the fPSC devices. Finally, future applications and the outlook for fPSCs are also discussed.

Perovskite solar cells (PSCs) are considered as one of the most promising alternatives for existing solar cells due to its excellent optoelectronic properties and high efficiency. However, lead has posed a serious issue due to its toxicity which may hinder the commercial use of lead‐based perovskite solar panels/arrays. There has been substantial work progress to find an environment‐friendly alternative metal ion to replace lead. Tin (Sn)‐based PSCs have been successfully synthesized and optimized with high efficiency, making it the most promising active material for lead‐free PSCs. In this review, the role of J–V hysteresis in tin halide PSCs is discussed from the perspective of system structure, working concepts, and interfacial carrier dynamics in detail. The problem of hysteresis in PSCs is closely linked to ion migration, ferroelectric effects, capacitive effects, and trap‐assisted recombination processes, which are highlighted in this review. Further, remediation to reduce the hysteresis by various strategies is explained for tin‐based perovskites. The core focus of this review is to analyze the deterioration of device performance and stability caused due to the generation of defects in the perovskite films, leading to a time‐dependent hysteresis of the current–voltage curves.

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