FAPbI 3 ‐Based Perovskite Solar Cells Employing Hexyl‐Based Ionic Liquid with an Efficiency Over 20% and Excellent Long‐Term Stability

Hybrid organic–inorganic halide perovskite based solar cell technology has passed through a phase of unprecedented growth in the efficiency scale from 3.8% to above 25% within a decade. This technology has drawn tremendous research interest because of facile solution processability, ease of large scale manufacturing and ultra-low cost production of perovskite based thin film solar cells. It has been observed that performances of perovskite-based solar cells are extremely dependent on the morphology and crystallinity of the perovskite layer. The high-quality perovskite films have made a significant impact on the fabrication of efficient and stable hybrid perovskite solar cells. It has also been observed that device lifetime depends on the perovskite morphology; devices with larger perovskite grains degrade slowly than those of the smaller ones. Various methods of perovskite growth such as sequential deposition, doctor blading, slot die coating and spray coating have been applied to achieve the most appropriate morphology necessary for highly efficient and stable solar cells. This review focuses on the recent progress in morphology optimizations by various processing condition such as annealing condition, additive effects, Lewis acid–base adduct approach, precursor solution aging and post-device ligand treatment emphasizing on grain sizes, film uniformity, defect passivation, ambient compatibility and device efficiency and stability. In this review, we also discussed recently developed bifacial stamping technique and deposition methods for large-area and roll-to-roll fabrication of highly efficient and stable perovskite solar cells.

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Recent progress in morphology optimization in perovskite solar cell

Perovskite solar cells have been at the center of intense research over the past decade. Efficiencies have gone from single digits to a certified 25.2%, an unprecedented improvement for any solar cell technology. At this stage, stability remains a concern regarding the suitability of these solar cells for commercialization. Here, we review recent developments in the use of carbon materials to improve the stability of perovskite solar cells. Incorporating carbon materials into perovskite solar cells promises to be revolutionary in the solar cell field, as degradation mechanisms are alleviated to achieve long-term stability making them attractive for commercialization.

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The role of carbon-based materials in enhancing the stability of perovskite solar cells

The defect passivation of perovskite films is an efficacious way to further boost the power conversion efficiency (PCE) and long-term stability of perovskite solar cells (PSCs). In this work, ionic...

Interface Engineering of Imidazolium Ionic Liquids toward Efficient and Stable CsPbBr3 Perovskite Solar Cells.

Emerging photovoltaics (PVs) focus on a variety of applications complementing large scale electricity generation. Organic, dye-sensitized, and some perovskite solar cells are considered in building integration, greenhouses, wearable, and indoor applications, thereby motivating research on flexible, transparent, semitransparent, and multi-junction PVs. Nevertheless, it can be very time consuming to find or develop an up-to-date overview of the state-of-the-art performance for these systems and applications. Two important resources for recording research cells efficiencies are the National Renewable Energy Laboratory chart and the efficiency tables compiled biannually by Martin Green and colleagues. Both publications provide an effective coverage over the established technologies, bridging research and industry. An alternative approach is proposed here summarizing the best reports in the diverse research subjects for emerging PVs. Best performance parameters are provided as a function of the photovoltaic bandgap energy for each technology and application, and are put into perspective using, e.g., the Shockley–Queisser limit. In all cases, the reported data correspond to published and/or properly described certified results, with enough details provided for prospective data reproduction. Additionally, the stability test energy yield is included as an analysis parameter among state-of-the-art emerging PVs.

https://onlinelibrary.wiley.com/doi/pdf/10.1002/aenm.202002774

Device Performance of Emerging Photovoltaic Materials (Version 1)

The preparation of high-quality perovskite films with low grain boundaries and defect states is a prerequisite for achieving high-efficiency perovskite solar cells (PSCs) with good environmental stability. An effective additive engineering strategy has been developed for simultaneous defect passivation and crystal growth of CsPbBr3 perovskite films by introducing 1,3,5-triazine-2,4,6-triamine (melamine) into the PbBr2 precursor solution. The resultant melamine-PbBr2 film has a loose, large-grained structure and decreased crystallinity, which has a positive effect on the crystallization process of the perovskite as it retards the crystallization rate as a result of the interaction between melamine and lead ions. Additionally, the passivation by melamine gives a high-quality CsPbBr3 perovskite film with fewer grain boundaries, lower defect densities, and better energy level matching is achieved by multistep liquid-phase spin-coating, which greatly suppresses the nonradiative recombination resulting from the defects and promotes charge extraction at the interface. A champion power conversion efficiency as high as 9.65 % with a promising open-circuit voltage of 1.584 V is achieved for PSCs with an architecture of fluorine-doped tin oxide/c-TiO2 /m-TiO2 /melamine-added CsPbBr3 /carbon-based hole-transporting layer. Furthermore, the unencapsulated melamine-added CsPbBr3 PSC shows superior thermal and humidity stability in ambient air at 85 °C or 85 % relative humidity over 720 h.

Grain Enlargement and Defect Passivation with Melamine Additives for High Efficiency and Stable CsPbBr3 Perovskite Solar Cells.

The favorable contact and matching energy level at the electrode/perovskite interface as well as the high-quality perovskite film are prerequisites for high photovoltaic performance perovskite solar cells (PSCs). Herein, an innovative interface engineering strategy has been proposed to modify TiO2 as well as the perovskite film simultaneously by introducing ammonium chloride (AC), which not only improves the contact and energy level matching at the TiO2/perovskite interface but also provides a high-quality perovskite film with larger grain size by regulating the crystallization kinetics of CsPbBr3. Furthermore, chlorine anions in AC tend to combine with TiO2 to passivate its surface defects; the ammonium cation can bond with the uncoordinated ionic defects of perovskite. As a result, a remarkably enhanced charge extraction and retarded charge recombination within inorganic CsPbBr3 PSCs is acquired through the interface engineering of AC, and the power conversion efficiency of the modified device is increased from the original 6.59% to 9.60%. By compensating the energy level at the perovskite/carbon interface by setting an efficient hole-transporting layer of zinc phthalocyanine (ZnPc), the best efficiency up to 10.12% was achieved for the device with AC and ZnPc interface modification, which is much higher than 7.87% efficiency for the ZnPc-only PSCs, further demonstrating the important positive effects of AC modification on device performance. Moreover, the optimized device without any encapsulation presents an exceptional long-term stability under persistent attack by 80% RH air atmosphere at 25 °C for 720 h.

Zekun Gong

Papers

Interface Engineering of Imidazolium Ionic Liquids toward Efficient and Stable CsPbBr3 Perovskite Solar Cells.

Grain Enlargement and Defect Passivation with Melamine Additives for High Efficiency and Stable CsPbBr3 Perovskite Solar Cells.

Improved charge extraction through interface engineering for 10.12% efficiency and stable CsPbBr3 perovskite solar cells

Enhanced charge extraction in carbon-based all-inorganic CsPbBr3 perovskite solar cells by dual-function interface engineering

Compositional Engineering of Chloride Ions Doped CsPbBr3 Halides for Highly Efficient and Stable All‐Inorganic Perovskite Solar Cells