L‐Arginine‐Doped PFN‐Br as a Cathode Interlayer for Conventional Organic Solar Cells

The cathode interlayer (CIL) plays a crucial role in organic solar cells (OSCs), which can establish an Ohmic contact between the active layer and the electrode, lower the electron extraction barriers, and minimize the charge carrier recombination. The CIL modification is a useful strategy for improving the performance of OSCs. Herein, an inexpensive water–alcohol‐soluble material known as L‐Arginine (L‐Arg) is introduced as a modifier for the PFN‐Br CIL, leading to successful optimization of the CIL quality. Following L‐Arg modification, the work function of the CIL is lowered and the electron extraction is facilitated. L‐Arg assists in exciton dissociation while suppressing both bimolecular and trap‐assisted recombination processes. The modified CIL establishes superior contact with the metal electrode due to its enhanced hydrophilicity, which helps electron collection. Consequently, the average power conversion efficiency increases from 10.54% in the reference device to 11.17% in the optimally doped device.