Hole-Transporting Low-Dimensional Perovskite for Enhancing Photovoltaic Performance.

Halide perovskites with low-dimensionalities (2D or quasi-2D) have demonstrated outstanding stabilities compared to their 3D counterparts. Nevertheless, poor charge-transporting abilities of organic components in 2D perovskites lead to relatively low power conversion efficiency (PCE) and thus limit their applications in photovoltaics. Here, we report a novel hole-transporting low-dimensional (HT2D) perovskite, which can form a hole-transporting channel on the top surface of 3D perovskite due to self-assembly effects of metal halide frameworks. This HT2D perovskite can significantly reduce interface trap densities and enhance hole-extracting abilities of a heterojunction region between the 3D perovskite and hole-transporting layer. Furthermore, the posttreatment by HT2D can also reduce the crystal defects of perovskite and improve film morphology. As a result, perovskite solar cells (PSCs) can effectively suppress nonradiative recombination, leading to an increasement on photovoltage to >1.20 V and thus achieving >20% power conversion efficiency and >500 h continuous illumination stability. This work provides a pathway to overcome charge-transporting limitations in low-dimensional perovskites and delivers significant enhancements on performance of PSCs.

Rapid Microwave-Annealing Process of Hybrid Perovskites to Eliminate Miscellaneous Phase for High Performance Photovoltaics.

Rapid processing technologies of perovskite solar cells (PSCs) offer an exciting approach to raise the rate of production. Herein, a rapid microwave-annealing process (MAP) is reported to replace the traditional hotplate annealing process (HAP) and the processing period of perovskite is reduced to less than 1 min. Benefiting from the penetrability and simultaneity of microwave irradiation, the MAP method can effectively eliminate miscellaneous phases and thus achieve >1 µm large-size crystal grains in perovskite films. These MAP treated perovskite films exhibit pure crystalline phase, long charge-carrier lifetime, and low defect density, which can substantially improve the PSC efficiency without requiring an additional enhancer/passivation layer. The inverted planar PSCs present enhanced power conversion efficiency from 18.33% (HAP) to 21.59% (MAP) and good stability of >1000 h lifetime without encapsulation under ambient conditions. In addition, MAP can be applied to a large-size (10 cm × 10 cm) perovskite film fabrication as well as a broader tolerance in environmental temperature and precursor concentration, making it a reliable method for repeatably practical fabrication of perovskite photovoltaics.

A Nontoxic Bifunctional (Anti)Solvent as Digestive-Ripening Agent for High-Performance Perovskite Solar Cells.

The preparation of high-quality perovskite films is important for achieving high-performance perovskite solar cells (PSCs). The effective balance between solvent and antisolvent is an essential factor for regulating high-quality perovskite film during the spin-coating and thermal-annealing steps. In this work, a greener, nonhalogenated, nontoxic bifunctional (anti)solvent, methyl benzoate (MB), is developed not only as an antisolvent to rapidly generate crystal seeds at the perovskite spin-coating step, but also as a digestive-ripening solvent for the perovskite precursors, which can prevent the loss of organic components during the thermal-annealing stage and effectively suppress the formation of miscellaneous lead halide phases. As a result, this novel bifunctional (anti)solvent is employed in planar n-i-p PSCs for engineering high-quality perovskite layers and thus achieving a power conversion efficiency up to 22.37% with negligible hysteresis and >1300 h stability. Moreover, due to the high boiling point and low-volatility characteristic of MB, high-performance PSCs are achieved reproducibly at different operating temperatures (22-34 °C). Therefore, this developed bifunctional solvent system can provide a promising platform toward globally upscaling and commercializing PSCs in all seasons and regions.

One-Step Synthesis of Aliphatic Potassium Acyltrifluoroborates (KATs) from Organocuprates.

A one-step synthesis of aliphatic KATs from organocuprates is reported. Organolithium and organomagnesium reagents were readily transmetalated onto Cu(I) and coupled with a KAT-forming reagent to yield the respective aliphatic KAT. The protocol is suitable for primary, secondary and-for the first time-tertiary alkyl substrates. These protocols considerably expand the range of KATs that can be readily accessed in one step from commercially available starting materials.

Synthesis of Bifunctional Potassium Acyltrifluoroborates.

New bifunctional potassium acyltrifluoroborate (KAT) substrates have been synthesized in gram scale using optimized reaction conditions. Chemoselective transformation of functional groups in the presence of an acyltrifluoroborate has been demonstrated, and orthogonal reactions of bifunctional KAT reagents are reported. This allows for the incorporation of KAT moieties into peptides and dyes.