Macromers for Encapsulating Perovskite Photovoltaics and Achieving High Stability

Abstract Perovskite solar cells (pero‐SCs) are highly unstable even under trace water. Although the blanket encapsulation (BE) strategy applied in the industry can effectively block moisture invasion, the commercial UV‐curable adhesives (UVCAs) for BE still trigger power conversion efficiency deterioration, and the degradation mechanism remains unknown. For the first time, the functions of commercial UVCAs are revealed in BE‐processed pero‐SCs, where the small‐sized monomer easily permeates to the perovskite surface, forming an insulating barrier to block charge extraction, while the high‐polarity moiety can destroy perovskite lattice. To solve these problems, a macromer, named PIBA is carefully designed, by grafting two acrylate terminal groups on the highly gastight polyisobutylene and realizes an increased molecular diameter as well as avoided high‐polarity groups. The PIBA macromer can stabilize on pero‐SCs and then sufficiently crosslink, forming a compact and stable network under UV light without sacrificing device performance during the BE process. The resultant BE devices show negligible efficiency loss after storage at 85% relative humidity for 2000 h. More importantly, these devices can even reach ISO 20653:2013 Degrees of protection IPX7 standard when immersed in one‐meter‐deep water. This BE strategy shows good universality in enhancing the moisture stability of pero‐SCs, irrespective of the perovskite composition or device structure.