Ink engineering for slot-die coated perovskite solar cells and minimodules

The power conversion efficiencies of perovskite solar cells (PSCs) have approached 26% for single-junction and 33% for multi-junction cells. Thus, various scalable depositions are studied to improve the manufacturability of PSCs for market entry. Of all types, slot-die coating is a promising technique thanks to its excellent compatibility with versatile systems. However, the complicated ink chemistry and film formation are major obstacles to scaling up devices. In this review, we systematically discuss ink engineering in the fabrication of slot-die-coated PSCs and perovskite minimodules, covering all functional layers that are processed using solution-based means. We then summarize a range of strategies to improve ink compatibility with slot-die coating, focusing on how to optimize the ink formulation to achieve high-quality films. Finally, we highlight the existing challenges and potential avenues for further development of slot-die-coated devices.