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Enhancing the quality of junctions is crucial for optimizing carrier extraction and suppressing recombination in semiconductor devices. In recent years, metal halide perovskite has emerged as the most promising next-generation material for optoelectronic devices. However, the construction of high-quality perovskite junctions, as well as characterization and understanding of their carrier polarity and density, remains a challenge. In this study, using combined electrical and spectroscopic characterization techniques, we investigate the doping characteristics of perovskite films by remote molecules, which is corroborated by our theoretical simulations indicating Schottky defects consisting of double ions as effective charge dopants. Through a post-treatment process involving a combination of biammonium and monoammonium molecules, we create a surface layer of n-type low-dimensional perovskite. This surface layer forms a heterojunction with the underlying 3D perovskite film, resulting in a favorable doping profile that enhances carrier extraction. The fabricated device exhibits an outstanding open-circuit voltage (V OC) up to 1.34 V and achieves a certified efficiency of 19.31% for single-junction wide-bandgap (1.77 eV) perovskite solar cells, together with significantly enhanced operational stability, thanks to the improved separation of carriers. Furthermore, we demonstrate the potential of this wide-bandgap device by achieving a certified efficiency of 27.04% and a V OC of 2.12 V in a perovskite/perovskite tandem solar cell configuration. [ABSTRACT FROM AUTHOR]

Tin halide perovskite solar cells are promising for the next generation of highly efficient photovoltaics. Their commercialization can be accelerated by increasing their stability in moisture and oxygen. Herein, an n‐type organic molecule (IO‐4Cl) is applied as an interlayer between the perovskite films and electron transport layers in p‐i‐n structured devices. The electron‐rich indacenodithieno‐[3,2‐b]thiophene enhances electron transport, while the hydrocarbon side chains and rigid conjugated backbone isolate air. It is also shown that the C═O in IO‐4Cl can coordinate with Sn2+ on perovskite films' surface and grain boundaries to enhance perovskite crystal stability. In addition, IO‐4Cl slows down crystallization dynamics, resulting in lower non‐radiation recombination. The moisture ingress in the perovskite films is tracked under high relative humidity (RH) and it is found that IO‐4Cl can mitigate moisture infiltration. Finally, the devices with IO‐4Cl maintain 95% of the initial power conversion efficiency after 1200 h of storage in a nitrogen‐filled glovebox, and their stability in ambient air (60–80% RH) is significantly improved against pristine devices, thus demonstrating the beneficial effects of IO‐4Cl interlayer on device stability. [ABSTRACT FROM AUTHOR]

Metal halide perovskite solar cells may work for application in extreme temperatures, such as those experienced under extraterrestrial conditions. However, device performances in extreme temperatures are poorly investigated. This work systematically explores the performance of perovskite solar cells between −160 and 150 °C. In situ grazing‐incidence wide‐angle X‐ray scattering discloses perovskite phase transition and crystal disordering as dominant factors for the temperature‐dependent device efficiency deterioration. It is shown that perovskite lattice strain and relaxation originating from extreme temperature variations are recoverable, and so are the perovskite structure and photovoltaic performances. This work provides insights into the functioning under extreme temperatures, clarifying bottlenecks to overcome and the potential for extraterrestrial applications. [ABSTRACT FROM AUTHOR]

The relatively lower crystallinity and random orientation of quantum well structures hinder carrier transport and limit the performance of formamidinium (FA) based low‐n 2D perovskite devices. In this work, the crystallization and quantum well orientation are fine tuned to achieve efficient low‐n FA based Ruddlesden–Popper perovskite solar cells. The effects of different ionic additives on the crystallization, orientation, and photovoltaic performance of FA based low‐n 2D perovskites are comparatively investigated. It is found that NH4+ and SCN− can significantly retard the heterogeneous crystallization of low‐n phases in the intermediate state, and drive the templated growth of quantum well structure with vertical orientation. The optimized photovoltaic device based on (BA)2(FA)3Pb4I13 achieved a power conversion efficiency (PCE) of 18.14%, setting the highest record for FA‐based low‐n 2D perovskite solar cells as far as it is known (average n = 4). The unencapsulated device exhibited excellent stability and maintained 93.3% of its original PCE at 85 °C, and 86.3% at 1 Sun illumination after 720 h in humid ambient condition. [ABSTRACT FROM AUTHOR]

Flexible perovskite solar cells (FPSCs) represent a promising technology in the development of next‐generation photovoltaic and optoelectronic devices. SnO2 electron transport layers (ETL) typically undergo significant cracking during the bending process of FPSCs, which can significantly compromise their charge transport properties. Herein, the semi‐planar non‐fullerene acceptor molecule Y6 (BT‐core‐based fused‐unit dithienothiophen [3,2‐b]‐pyrrolobenzothiadiazole derivative) is introduced as the buffer layer for SnO2‐based FPSCs. It is found that the Y6 buffer layer can enhance the ability of charge extraction and bending stability for SnO2 ETL. Moreover, the internal stress of perovskite films is also reduced. As a result, SnO2/Y6‐based FPSCs achieved a power conversion efficiency (PCE) of 20.09% and retained over 80% of their initial efficiency after 1000 bending cycles at a curvature radius of 8 mm, while SnO2‐based devices only retain 60% of their initial PCE (18.60%) upon the same bending cycles. In addition, the interfacial charge extraction is also effectively improved in conjunction with reduced defect density upon incorporation of Y6 on the SnO2 ETL, as revealed by femtosecond transient absorption (Fs‐TA) measurements. [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]