An Alcohol‐Soluble N‐Annulated Perylene Diimide Cathode Interlayer for Air‐Processed, Slot‐Die Coated Organic Photovoltaic Devices and Large‐Area Modules

Abstract

Cathode interlayers (CILs) in organic photovoltaics (OPVs) are actively being researched as they are critical for device stability and performance. Herein, N‐annulated perylene diimide with a 2‐ethyl‐hexyl side chain (PDIN‐EH) is demonstrated, which is facile to synthesize as compared with conventional CILs such as PFN‐Br, exhibits solubility, and subsequent processability from ethanol. The PDIN‐EH is evaluated as a CIL in an air‐processed, slot‐die coated OPV consisting of PEDOT:PSS as the hole transport layer, PM6:Y6C12 as the bulk heterojunction, and top silver cathode electrode. All the organic layers are slot‐die coated from green solvents and devices achieve a power convention efficiency of more than 12%, a result that is among the best reported under ambient conditions for printed OPVs. Microscopy images reveal that the PDIN‐EH affords smooth film formation when slot‐die coated on top of PM6:Y6C12 bulk heterojunction for an improved contact with the Ag electrode. Furthermore, the fabrication of large‐area OPV modules on glass and flexible (polyethylene terephthalate) substrates is successfully demonstrated, with five cells connected in series achieving efficiency over 7% and open‐circuit voltage over 3.5 V. Herein, useful guidelines for achieving fully printed organic electronic devices from green solvents at a potential industrial scale are provided.