Recent progress towards roll-to-roll manufacturing of perovskite solar cells using slot-die processing

The power conversion efficiency of perovskite solar cells (PSCs) has recently reached 24.2% [1], the threshold for serious commercial interest, triggering an intense search for prospective large-scale production methods that will enable a swift transition from the laboratory to industrial-scale manufacture. Several industrially-compatible scalable methods have been deployed to fabricate PSCs, but the efficiencies of devices prepared using these methods remain inferior to devices prepared in the laboratory using spin coating, a technique that is unsuitable for large-scale manufacturing. A key challenge for the successful commercialization of PSCs is the production of highly uniform, pinhole-free films over a sufficiently large area while also controlling the crystallization process. Researchers in private and public sector organizations are devoting tremendous effort to overcoming these hurdles. Among the reported scalable methods, use of slot-die coating in sheet-to-sheet (S2S, batch) or roll-to-roll (R2R, continuous) processes is attractive for large-scale, low-cost manufacturing of PSCs, particularly on flexible substrates. In this review, we summarize recent advances in low-temperature S2S and R2R slot-die coating processes for PSCs, outline the key processing parameters controlling PSC fabrication and their impact on device performance, and describe current challenges and future prospects.