The stabilization of black-phase formamidinium lead iodide (α-FAPbI3) perovskite under various environmental conditions is considered necessary for solar cells. However, challenges remain regarding the temperature sensitivity of α-FAPbI3 and the requirements for strict humidity control in its processing. Here we report the synthesis of stable α-FAPbI3, regardless of humidity and temperature, based on a vertically aligned lead iodide thin film grown from an ionic liquid, methylamine formate. The vertically grown structure has numerous nanometer-scale ion channels that facilitate the permeation of formamidinium iodide into the lead iodide thin films for fast and robust transformation to α-FAPbI3. A solar cell with a power-conversion efficiency of 24.1% was achieved. The unencapsulated cells retain 80 and 90% of their initial efficiencies for 500 hours at 85°C and continuous light stress, respectively.

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In our day-to-day lives, advances in lightweight and flexible photovoltaics will promote a new generation of soft electronics and machines requiring high power-per-weight. Ultrathin flexible perovskite solar cells (F-PSCs) with high power-per-weight have displayed a unique potential for specific applications where lower weight, higher flexibility, and conformability are indispensable. This Review highlights the recent progress and practical applications of ultrathin and lightweight F-PSCs and demonstrates the routes toward enhanced device efficiency and improved mechanical and environmental stability concerning the choice of flexible substrates and the development of high-performance functional layers and flexible transparent electrodes. The fabrication technologies for mass production of efficient F-PSCs at large scale are then summarized, including continuous roll-to-roll methods integrated with low-temperature process. Furthermore, the practical applications focused on self-powered wearable electronic devices, solar-powered miniature unmanned aerial vehicles, and even solar modules operating in near-space are elaborated. Finally, the current challenging issues and future perspective are discussed, aiming to promote more extensive applications and commercialization processes for lightweight F-PSCs.

White organic light‐emitting diodes (WOLEDs) are highly attractive in the fields of solid‐state lighting. The biggest challenge that is facing at present is how to maximize the exciton utilization to further enhance the efficiency, while taking into account the stability. Here, highly efficient all‐fluorescence and fluorescence/phosphorescence (F/P) hybrid WOLEDs with low efficiency roll‐off by designing exciplex‐sandwich emissive architecture and precisely manipulating the exciton allocation are demonstrated. The resulting complementary‐color hybrid WOLEDs realize the maximum external quantum efficiency of 28.3% and power efficiency of 102.9 lm W−1, and remain 26.9% and 73.5 lm W−1 at 500 cd m−2 and yet as high as 25.8% and 63.5 lm W−1 at 1000 cd m−2, respectively, revealing very low roll‐off. By using the efficient blue exciplex combined with red and green phosphorescent emitters, the three‐color WOLEDs yield a high color rendering index of 86, an external quantum efficiency of 29.4%, and a power efficiency of 75.5 lm W−1. It is anticipated that the exciplex engineering will open an efficient avenue to precisely allocate excitons, and finally producing high‐performance WOLEDs for next‐generation solid‐state lighting technology.