Suppression of Coffee‐Ring Effect in Air‐Processed Inkjet‐Printed Perovskite Layer toward the Fabrication of Efficient Large‐Sized All‐Printed Photovoltaics: A Perovskite Precursor Ink Concentration Regulation Strategy

Inkjet‐printing technology is anticipated to play a forefront role in the future prototyping of perovskite solar cells (PSCs) to enable their ultralow‐cost and scalable manufacturing. However, key inkjet challenges related to fluid dynamics should be first addressed to allow the fabrication of high‐quality printed materials and subsequently competitive photovoltaics to the established market. Herein, piezoelectric drop‐on‐demand inkjet‐printing is employed with the aim of developing high‐efficiency, stable, and reproducible large‐sized all‐printed perovskite modules under ambient atmospheric conditions. The focus of this work is put on the study of the influence of perovskite precursor ink concentration on the jet‐ability of the ink, on the wettability of the substrate by the ink, as well as on the characteristics of the inkjet‐printed perovskite layers and correspondingly of the PSCs. The results show that by employing a facile and universal perovskite precursor ink concentration regulation strategy, the coffee‐ring effect (recorded by in situ video microscopy) is greatly suppressed, leading to the fabrication of much better quality perovskite layers and correspondingly more efficient and stable photovoltaics. Finally, the development of all‐printed carbon‐based hole‐transport‐material‐free perovskite submodules is demonstrated, along with low upscaling efficiency losses (8.1%rel dec −1 ) and outstanding stability (<5% performance degradation after 1000 h of ageing).