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Formamidinium‐lead triiodide (FAPbI3) perovskite holds promise as a prime candidate in the realm of perovskite photovoltaics. However, the photo‐active α‐FAPbI3 phase, existing as a metastable state, is observable solely at elevated temperatures and is susceptible to degradation into the δ‐phase in ambient air. Therefore, the attainment of phase‐stable α‐FAPbI3 in ambient conditions has become a crucial objective in perovskite research. Here, we proposed an efficient conversion process of PbI2 into the α‐FAPbI3 perovskites in ambient air. This conversion was facilitated by the introduction of chelating molecules, which interacted with PbI2 to form an intermediate phase. Due to the reduced formation barrier resulting from the altered reaction pathway, this stable intermediate phase transitioned directly into α‐FAPbI3 upon the deposition of the organic cation solution, effectively bypassing the formation of δ‐FAPbI3. Consequently, the ambient‐fabricated FAPbI3 perovskite solar cells (PSCs) exhibited an outstanding power conversion efficiency of 25.08 %, along with a high open‐circuit voltage of 1.19 V. Furthermore, the unencapsulated devices demonstrated remarkable environmental stability. Notably, this innovative approach promises broad applicability across various chelating molecules, opening new avenues for further progress in the ambient air fabrication of FAPbI3 PSCs. [ABSTRACT FROM AUTHOR]

As a fundamental thermodynamic parameter, pressure serves as an effective tool to control the structures and properties of functional materials. To date, numerous pressure‐engineering methods have been introduced to enhance perovskite structures and devices. This paper comprehensively reviews the advances in understanding the effects of pressure on perovskite materials and devices, encompassing both low and high‐pressure influences. These effects are categorized into six distinct groups based on their underlying mechanisms, detailing the evolution of perovskite structures from macroscopic to microscopic levels, and exploring the interplay between these structures and their functional characteristics. Finally, the current challenges and offer insights into the future prospects for harnessing pressure effects to further develop perovskite structures, properties, and devices are assessed. [ABSTRACT FROM AUTHOR]

Firms with higher R&D intensity subsequently experience higher stock returns in international stock markets, highlighting the role of intangible investments in international asset pricing. The R&D effect is stronger in countries where growth option risk is more likely priced, but is unrelated to country characteristics representing market sentiments and limits-of-arbitrage. Moreover, we find that R&D intensity is associated with higher future operating performance, return volatility, and default likelihood. Our evidence suggests that the cross sectional relation between R&D intensity and stock returns is more likely attributable to risk premium than to mispricing. [ABSTRACT FROM AUTHOR]

The two‐step sequentially deposition strategy has been widely used to produce high‐performance FAPbI3‐based solar cells. However, due to the rapid reaction between PbI2 and FAI, a dense perovskite film forms on top of the PbI2 layer immediately and blocks the FAI diffusion into the bottom of the PbI2 film for a complete reaction, which results in a low‐efficiency and limited reproducibility of perovskite solar cells (PSCs). Here, high‐quality α‐FAPbI3 perovskite films by crystal growth regulation with 4‐fluorobenzamide additives is fabricated. The additives can interact with FAI to suppress the fast reaction between the FAI and PbI2 and effectively passivate the under‐coordinated Pb2+ or I‐ defects. As a result, α‐FAPbI3 perovskite films with low trap density and large grain size are prepared. The modified PSCs present a high‐power conversion efficiency of 24.08%, maintaining 90% of their initial efficiency after 1400 h in high humidity. This study provides an efficient strategy of synergistic crystallization and passivation to form high‐quality α‐FAPbI3 films for high‐performance PSCs. [ABSTRACT FROM AUTHOR]

Intercalation regulation is a special way to tune the photophysical properties of perovskite without changing the organic cations. Here, it is found that dimethyl sulfoxide can be effectively intercalated into synthesized (OHC6H5CH2CH2NH3)2PbBr4 perovskite through hydrogen bonds between organic spacer layers and solvent molecules. The new intercalated perovskite can be stored for more than two months under a relative humidity of about 60% at room temperature without encapsulation. The single crystal microwire array device based on this special structure presents photoelectric response of a light on/off ratio of 400 under 365 nm irradiation at 3 V. The device has a low dark current of 10−13 A. Moreover, the inserted solvent molecules can be removed from the perovskite or reinserted into the perovskite under different processing conditions. The results show the potential to regulate the optoelectronic properties of perovskites by reversibly binding intercalated molecules with perovskites. [ABSTRACT FROM AUTHOR]