In the past decade, perovskite solar cells (PSCs) have made significant progress, becoming a promising class of photovoltaic devices for commercialization. Achieving large-area, high-efficiency perovskite modules is key to their commercialization. To date, small-area PSCs based on α-FAPbI₃ have achieved a certified efficiency of 26.1%. However, the efficiency of corresponding perovskite modules is still low, mainly due to poor quality of large-area perovskite films.

Meniscus coating methods, including blade and slot-die coating, are favored for their simplicity, cost-effectiveness and high throughput, which is ideal for scaling up perovskite films. However, these methods are strongly influenced by precursor solution viscosity and concentration, solvent boiling points and vapor pressures, and specific process parameters. The interaction among these factors significantly impacts perovskite crystallization growth, and their effective regulation is crucial for large-scale, high-quality perovskite films. Recently, Huang Chunjie, Tan Shan and Yu Bingcheng in Prof. Meng qingbo and Prof. Li Dongmei’s group from Institute of Physics, Chinese Academy of Sciences, have developed a meniscus-modulated blade coating method combined with a high-concentration precursor solution to upscale high-quality perovskite films, and fabricated small-area cells (0.09cm²) with notable 25.31% efficiency and 12.4cm² FAPbI₃ minimodules with certified 23.1% efficiency. 

Researchers compared coordination interactions of low-boiling-point, high-saturated-vapor-pressure solvents (such as MOE) and high-boiling-point, low-saturated-vapor-pressure solvents (such as DMF) for precursor solutions. These solvents are more challenging to evaporate during the blade-coating process, resulting in slower heterogeneous nucleation. This contributes to the preparation of large-grain, high-quality FAPbI₃ films. However, the slow drying of liquid films caused by DMF solvent leads to poor uniformity and coverage of final perovskite films. Additionally, it is difficult to thin blade-coated perovskite films for suitable thickness, which adversely affects nucleation and crystallization of the perovskite films as well as subsequent carrier transport in the devices. To address these issues, the researchers developed a meniscus-modulated blade-coating technique. Unlike traditional blade-coating methods, this technique utilizes high-speed airflow to modulate the meniscus in the blade-coating process, effectively reducing the amount of solution dragged out from the meniscus due to viscous forces and Marangoni flow, thereby achieving the thinning of the liquid film and the final perovskite film. This allows for relatively higher concentration of the perovskite precursor solution based on the DMF system. This meniscus-modulated blade-coating technique, combined with high-concentration precursor solutions, facilitates the growth of black-phase FAPbI₃ films with large grain sizes, high crystal orientation and good uniformity. 

This study entitled "Meniscus-modulated blade coating enables high-quality a-phase formamidinium lead triiodide crystals and efficient perovskite minimodules" was published on Joule.

This work was supported by the Ministry of Science and Technology of China, Natural Science Foundation of China, Beijing Natural Science Foundation and CAS-CSIRO Joint Project.