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Perovskite solar cells (PSCs) have the potential for widespread application, but challenges remain for a reliable characterization of their performance. Standardized protocols for measuring and reporting are still debated. Focusing on the short circuit current density (JSC), current–voltage characteristics (J–V) and external quantum efficiency (EQE) are collected to estimate the parameter. Still, they often provide a mismatch above 1 mA cm−2, resulting in a possible 5% or higher error. Combining experimental data and optical simulations, it is demonstrated that the EQE can provide a reliable estimate of the JSC that could otherwise easily be overestimated by J–V. With access to the internally transmitted light through simulations, an upper limit for EQE is defined depending on the front layers. Details on the origin of the spectral shape and contributions to the optical losses are obtained with further optical simulations, providing hints for cell optimization to achieve a photocurrent gain. The authors use solution‐processed n‐i‐p PSCs with triple‐cation mixed‐halide absorbers as demonstrators and ultimately come to the proposal of an upgrade of the present best practices in PSC efficiency measurements. Still, the approach and conclusions are general and apply to cells with all designs and chemical formulations. [ABSTRACT FROM AUTHOR]

The power conversion efficiency of the formamidinium tin iodide (FASI) solar cells constantly increases, with the current record power conversion efficiency approaching 15%. The literature reports a broad anomaly distribution of the photoluminescence (PL) peak position. The PL anomaly is particularly relevant to photovoltaic applications since it directly links the material's bandgap and subgap defects energy, which are crucial to extracting its full photovoltaic potential. Herein, the PL of FASI polycrystalline thin film and powder is studied. It is found that a distribution of PL peak positions in line with the distribution available in the literature systematically. The distribution in PL is linked to the octahedral tilting and Sn off‐centering within the perovskite lattice, influenced by the procedure used to prepare the material. Our finding paves the way toward controlling the energy distribution of tin perovskite and thus preparing highly efficient tin halide perovskite solar cells. [ABSTRACT FROM AUTHOR]

In just over a decade, the power conversion efficiency of metal‐halide perovskite solar cells has increased from 3.9% to 25.5%, suggesting this technology might be ready for large‐scale exploitation in industrial applications. Photovoltaic devices based on perovskite single crystals are emerging as a viable alternative to polycrystalline materials. Perovskite single crystals indeed possess lower trap state densities, higher carrier mobilities, and longer diffusion lengths, and potentially can achieve higher performance with respect to those fabricated with polycrystalline films, although their integration in a complete device needs particular attention and the use of specifically tailored growth techniques. In this review, recent advances on single‐crystal halide perovskites are reported. First, crystalline structure and fundamental properties of 3D perovskites are discussed, including the emerging mixed‐anion cation perovskites, and then the most popular growth methods with a focus on techniques that enable the implementation in photovoltaic devices are presented. Architectures and materials used to produce lateral and vertical solar cells are further introduced and recent improvements in device design and fabrication are summarized. Finally, the strategies used to solve the still open challenge on these materials regarding stability under environmental conditions are critically discussed and the view on the opportunities offered by halide perovskites is reflected. [ABSTRACT FROM AUTHOR]

Tin is the frontrunner for substituting toxic lead in perovskite solar cells. However, tin suffers the detrimental oxidation of SnII to SnIV. Most of reported strategies employ SnF2 in the perovskite precursor solution to prevent SnIV formation. Nevertheless, the working mechanism of this additive remains debated. To further elucidate it, we investigate the fluoride chemistry in tin halide perovskites by complementary analytical tools. NMR analysis of the precursor solution discloses a strong preferential affinity of fluoride anions for SnIV over SnII, selectively complexing it as SnF4. Hard X‐ray photoelectron spectroscopy on films shows the lower tendency of SnF4 than SnI4 to get included in the perovskite structure, hence preventing the inclusion of SnIV in the film. Finally, small‐angle X‐ray scattering reveals the strong influence of fluoride on the colloidal chemistry of precursor dispersions, directly affecting perovskite crystallization. [ABSTRACT FROM AUTHOR]

Tin halide perovskites attract incremental attention to deliver lead‐free perovskite solar cells. Nevertheless, disordered crystal growth and low defect formation energy, related to Sn(II) oxidation to Sn(IV), limit the efficiency and stability of solar cells. Engineering the processing from perovskite precursor solution preparation to film crystallization is crucial to tackle these issues and enable the full photovoltaic potential of tin halide perovskites. Herein, the ionic liquid n‐butylammonium acetate (BAAc) is used to tune the tin coordination with specific O...Sn chelating bonds and NH...X hydrogen bonds. The coordination between BAAc and tin enables modulation of the crystallization of the perovskite in a thin film. The resulting BAAc‐containing perovskite films are more compact and have a preferential crystal orientation. Moreover, a lower amount of Sn(IV) and related chemical defects are found for the BAAc‐containing perovskites. Tin halide perovskite solar cells processed with BAAc show a power conversion efficiency of over 10%. This value is retained after storing the devices for over 1000 h in nitrogen. This work paves the way toward a more controlled tin‐based perovskite crystallization for stable and efficient lead‐free perovskite photovoltaics. [ABSTRACT FROM AUTHOR]

Lead (Pb) is one of the most toxic elements in existence and has been used by humans for thousands of years. With only a few exceptions, each widespread application of lead has been banned systematically due to dramatic environmental and health consequences. However, we are now at the dawn of the perovskite era, potentially requiring yet again the widespread application of lead. [ABSTRACT FROM AUTHOR]

Keywords: lead-free systems; perovskite solar cells; tin fluoride; tin halide perovskites; tin oxidation EN lead-free systems perovskite solar cells tin fluoride tin halide perovskites tin oxidation 21595 21595 1 09/16/21 20210920 NES 210920 B The crystallization b of tin-based perovskites is improved thanks to the fluoride in SnF SB 2 sb . Lead-free systems, perovskite solar cells, tin fluoride, tin halide perovskites, tin oxidation Inside Back Cover: Fluoride Chemistry in Tin Halide Perovskites (Angew. [Extracted from the article]

Daily temperature variations induce phase transitions and lattice strains in halide perovskites, challenging their stability in solar cells. We stabilized the perovskite black phase and improved solar cell performance using the ordered dipolar structure of b-poly(1,1-difluoroethylene) to control perovskite film crystallization and energy alignment. We demonstrated p-i-n perovskite solar cells with a record power conversion efficiency of 24.6% over 18 square millimeters and 23.1% over 1 square centimeter, which retained 96 and 88% of the efficiency after 1000 hours of 1-sun maximum power point tracking at 25° and 75°C, respectively. Devices under rapid thermal cycling between −60° and +80°C showed no sign of fatigue, demonstrating the impact of the ordered dipolar structure on the operational stability of perovskite solar cells. [ABSTRACT FROM AUTHOR]