Macromers for Encapsulating Perovskite Photovoltaics and Achieving High Stability.

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.