Mixed organic–inorganic halide perovskite solar cells have reached unprecedentedly high efficiency in a short term. Two major challenges in its large-scale deployment is the material instability and hazardous lead waste. Several studies have identified that lead replacement with its other alternatives does not show the similar assurance. In this manuscript, we introduce the concept of recycling of the degraded perovskite film (PbI 2 ), gaining back the initial optoelectronic properties as the best possible solution to avoid lead waste. The simple recycling procedure allows the utilization of some of the most expensive (fluorine-doped tin oxide), primary energy-consuming (TiO 2 ), and toxic (Pb) parts of the solar cell, reducing the payback time even further. This addresses the major issues of instability and expensive toxic lead disposal, altogether. We have demonstrated the comparative study of feasibility of recycling in degraded perovskite films deposited by three different standard fabrication routes. Films fabricated via acetate route shows efficient recycling compared to the other routes, i.e., chloride and sequential deposition routes. Moreover, recycling in sequentially deposited films needs further optimization.

Despite the remarkable efficiencies of perovskite solar cells, moisture instability has still been the major constraint in the technology deployment. Although, some research groups have discussed the possible mechanisms involved in the perovskite degradation, no broader understanding has been developed so far. Here, we demonstrate that the crystal orientation of perovskite film plays a major role in its degradation. We observed that the films fabricated via different routes led to different degradation behaviors and unraveled that diversity in the degradation rate arises due to the difference in crystallographic characteristics of the films. Using optical and electrical measurements, we show that the film prepared via a single-step (lead chloride precursor based) route undergoes a much faster degradation rate as compared with films prepared using single step (acetate precursor based) and two-step (or sequential deposition) routes. Although the resulting film is methylammonium lead iodide (MAPbI 3 ) regardless of processing via different routes, their respective crystal orientation is different. In this manuscript, we correlate crystal orientation of MAPbI 3 with their degradation pattern. Our studies also suggest a possible way to make stable perovskite film.

Abstract:For any given technology to be successful, its ability to compete with the other existing technologies is the key. Over the last five years, perovskite solar cells have entered the research spectrum with tremendous market prospects. These cells provide easy and low cost processability and are an efficient alternative to the existing solar cell technologies in the market. In this review article, we first go over the innovation and the scientific findings that have been going on in the field of perovskite solar cells (PSCs) and then present a short case study of perovskite solar cells based on their energy payback time. Our review aims to be comprehensive, considering the cost, the efficiency, and the stability of the PSCs. Later, we suggest areas for improvement in the field, and how the future might be shaped.

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Fully inorganic CsPbI 3 perovskite has been widely explored as an alternative light-harvesting material owing to its superior thermal stability over the organic−inorganic halide perovskite and the suitable band gap. However, stabilization of the photoactive CsPbI 3 phase at room temperature (RT) remains the biggest challenge. The photoactive α-CsPbI 3 which requires high-temperature synthesis (above 320 °C) transforms into the photoactive γ-CsPbI 3 at RT and on exposure to ambient rapidly transforms into the non-photoactive δ-CsPbI 3 . Herein, we investigate the effect of incorporating Mg 2+ in the CsPbI 3 lattice. It has been found that the photoactive γ-phase of CsPbI 3 can be stabilized for more than 167 days at RT in a nitrogen atmosphere by incorporating Mg 2+ inside the lattice. Incorporating Mg 2+ inside the lattice of CsPbI 3 has led to enhanced optoelectronic properties along with enhanced phase and thermal stability.

Organic−inorganic hybrid lead halide perovskites have shown significant progress in the last few years having achieved efficiencies over 25% at the lab scale. The sequential deposition technique has provided a robust approach in the perovskite film fabrication. However, obtaining a reproducible and quality perovskite film has always been challenging because of the highly crystalline and ordered (001) oriented underlying PbI 2 film. Here, we report a simple solution approach to fabricate a PbI 2 residue-free, superior grade perovskite film by using a compositional engineered PbI 2 −precursor solution. We demonstrate that the Pb−precursor film crystallized into a R-centered Hexagonal metric lattice with (h0l), (hk0), and (00l) orientations provides a more efficient and quicker conversion into perovskites compared to conventional (001) oriented 2H-PbI 2 . A porous and multi-oriented PbI 2 film is prepared by rationally incorporating a volumetric fraction of Pb(Ac) 2 •3H 2 O in the typical PbI 2 /dimethylformamide precursor solution, which significantly improves the surface features of PbI 2 as well as the structural properties. As a result, a compact, smooth, and large grain perovskite can be obtained by accomplishing a full conversion with comparatively much less reaction time. Furthermore, a comprehensive mechanism of structural modification of PbI 2 and the role of its orientation in ameliorating the reaction kinetics has been demonstrated.

Sequential deposition route is widely investigated in fabricating perovskite thin films for state‐of‐the‐art perovskite photovoltaics. However, concerns such as lower morphological control, phase purity, and remnant unreacted salts methylammonium iodide (MAI and PbI2) are raised, which can significantly deteriorate optoelectronic properties, hence the operational durability of the devices. Herein, a facile two‐step method to prepare high‐quality perovskite thin films with reproducibility is reported, as‐spun PbI2 is annealed at varying thermal input under controlled rate, and a trend in converted perovskite film properties is noted. Specifically, PbI2 thin film annealed at 200 °CC results in 20x intensified crystallinity with pinholes free and a subsequent reduction in the crystal microstrain. In addition, it provides higher surface roughness to load more MAI [in iso‐propyl alcohol (IPA)]; therefore, a higher perovskite conversion is achieved. This method enables a significant efficiency enhancement in the treated sample (Pero@PbI2‐200 °C) as compared with controlled film; it retains around 90% initial efficiency after 384 h of ambient exposure. Furthermore, a facile intermediate solvent treatment method to gain the complete conversion of PbI2 into perovskite is also reported. This study highlights the importance of morphological control in governing optoelectronic properties, hence the efficiency and stability of perovskite solar cells.

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