In this work, we reviewed the evolution of the performance of photovoltaic devices (single junction and tandems) using Sn-containing perovskites.

Solution-processed organic-inorganic halide perovskites are currently established as the hottest area of interest in the world of photovoltaics, ensuring low manufacturing cost and high conversion efficiencies. Even though various fabrication/deposition approaches and device architectures have been tested, researchers quickly realized that the key for the excellent solar cell operation was the quality of the crystallization of the perovskite film, employed to assure efficient photogeneration of carriers, charge separation and transport of the separated carriers at the contacts. One of the most typical methods in chemistry to crystallize a material is anti-solvent precipitation. Indeed, this classical precipitation method worked really well for the growth of single crystals of perovskite. Fortunately, the method was also effective for the preparation of perovskite films by adopting an anti-solvent dripping technique during spin-coating the perovskite precursor solution on the substrate. With this, polycrystalline perovskite films with pure and stable crystal phases accompanied with excellent surface coverage were prepared, leading to highly reproducible efficiencies close to 22%. In this review, we discuss recent results on highly efficient solar cells, obtained by the anti-solvent dripping method, always in the presence of Lewis base adducts of lead(II) iodide. We present all the anti-solvents that can be used and what is the impact of them on device efficiencies. Finally, we analyze the critical challenges that currently limit the efficacy/reproducibility of this crystallization method and propose prospects for future directions.

Lead halide perovskites of the type APbX3 (where A = methylammonium MA, formamidinium FA, or cesium and X = iodide and bromide), in a single‐crystal form or more often as polycrystalline films, have already shown unique optoelectronic properties, comparable with those of the best single‐crystal semiconductors. To form a properly crystalline iodide or iodide/bromide, perovskite and achieve high performance in solar cells, sources containing only iodide and bromide salts (PbI2, PbBr2, MAI, FAI, CsI, MABr) are typically used as precursor materials. However, recently, most of the record perovskites contain MACl as additive to control their crystallization, revisiting the importance of methylammonium cation excess and chloride incorporation in perovskites, previously highlighted by Snaith's group back in 2012. Here, we review the background and recent progress in MACl‐mediated crystallization of perovskites, as well as the impact of the additive in solar cells. In particular, we describe the current understanding of the mechanism of perovskite crystallization process and defect passivation at grain boundaries in the presence of MACl. We then discuss the spectacular results (in terms of record efficiencies, stability, and up‐scaling) that have been delivered by solar cells employing MACl‐incorporated perovskites, and give an outlook of future research avenues that might bring perovskite solar cells closer to commercialization.

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In this review, we present the most characteristic photoactive perovskites that can be formed with the help of d-block metals.

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Fluorine plasma treatment was investigated as an appropriate means for the surface modification of TiO 2 thin film electrodes and the optimization of their performance as photoanodes in dye solar cells (DSCs) employing the Co(II)/ (III) redox shuttle and the organic D35 sensitizer. Detailed surface and structural characterization of the titania films by contact angle measurements, atomic force microscopy, profilometry, and Raman and UV−vis spectroscopy showed that high density SF 6 plasma provoked severe film densification and thus an increase of the nanoparticles packing density, leaving intact the crystallinity, particle size, and optical bandgap. Surface fluorination of the TiO 2 films was also identified by X-ray photoelectron spectroscopy. The combination of the above effects resulted in the enhancement of both photocurrent and power conversion efficiency of the corresponding DSCs at moderate plasma treatment durations, while the photovoltage decreased continuously as a function of the fluorine processing time. Electrochemical impedance spectroscopy analysis revealed a marked increase of the density and distribution of trap states due to fluorine induced surface states along with a systematic downward shift of the TiO 2 conduction band, probably attributed to the electrostatic coupling of intercalated Li + cations with the polar Ti−F species at the TiO 2 surface, in agreement with the V oc drop. In contrast, enhanced electron injection was inferred to underlie the observed J sc and DSC performance improvements, as surface fluorination and the concomitant film densification slightly increased electron transport while hardly affecting dye loading capacity, light harvesting efficiency, and recombination kinetics, except for the case of prolonged plasma treatment. Effective control of the detrimental side effects of fluorine species can render this kind of plasma treatment a powerful method to tune the surface and electrical properties of TiO 2 films and optimize the behavior and performance of the resulting DSC devices.