Photo-Crosslinkable Naphthalene Diimide Polymer for Solution-Processed n–i–p Perovskite Solar Cells

• Published in: Chemistry of materials 2024-01, Vol.36 (2), p.795-802
• Main Authors: Shi, Yangwei, McCarthy, Declan P., Lungwitz, Dominique, Jiang, Fangyuan, Taddei, Margherita, Contreras, Hannah, Lin, Yujing, Mohapatra, Aiswarya Abhisek, Tang, Kan, Zhang, Yadong, Barlow, Stephen, Kahn, Antoine, Marder, Seth R., Ginger, David S.
• Format: Article
• Language: English
• Subjects: Aromatic compounds; Hydrocarbons; INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; Perovskites; Polymers; Solar cells; SOLAR ENERGY
• ISSN: 0897-4756; 1520-5002
• DOI: 10.1021/acs.chemmater.3c02295

We copolymerize a norbornene monomer bearing a pendant naphthalene diimide with a norbornene bearing a cinnamate pendant moiety to synthesize a crosslinkable electron-transporting polymer and study its use in solution-processed n–i–p perovskite solar cells. The crosslinked material exhibits over 90% transparency in the visible region and higher thermal stability (>300 °C) and lower surface energy than the corresponding homopolymer of the naphthalene diimide functionalized norbornene. Coating an ITO surface with the photo-crosslinked copolymer yields a slightly lower work function than homopolymer-coated ITO. We show that the morphologies of the perovskite films deposited on both polymers are similar (∼300 nm features) based upon scanning electron microscopy. Our solar-cell device results show that the crosslinked naphthalene diimide polymer gives a higher open-circuit voltage (1.08 vs 1.05 V), fill factor (average 64.43 vs 58.77%), and stabilized power conversion efficiency (12.28 vs 10.33%) compared to its non-crosslinked homopolymer counterpart, as well as reduced hysteresis. We attribute the improved performance to decreased work function, reduced nonradiative recombination, and higher shunt resistance.