A novel naphthalene diimide-based conjugated polymer as an electron transport material for non-fullerene organic solar cells

Abstract

Electron transport materials (ETMs) play an important role in organic solar cells (OSCs) and the rapidly evolving non-fullerene acceptors have higher demands for ETMs. A novel naphthalene diimide-based conjugated polymer (PNDI-NN) with aliphatic amino side chains at the N-position of naphthalene diimide was synthesized and introduced as an ETM in non-fullerene OSCs. The only N-substituted aliphatic amino side chains endow PNDI-NN with good solubility in alcohol and an intense self-doping effect, which can not only reduce the work function of the metal electrode (Ag), but also have a good coverage on the active layer and promote electron transport. The device with PNDI-NN showed the best power conversion efficiency of 15.6% with an improved open-circuit voltage (V_OC) and fill factor (FF). The device also exhibited good long-term stability in an inert atmosphere, in a humid environment and under continuous heating.