High Open-Circuit Voltage Organic Photovoltaics Fabricated Using an Alkylidene Fluorene Derivative as a Non-fullerene Acceptor

Alkylidene fluorene-based molecular acceptors, AF-T-INCN and AF-T8-INCN, are synthesized for use in non-fullerene organic photovoltaics. Both AF-T-INCN and AF-T8-INCN exhibited absorption region from 400 to 700?nm in their neat film states. Highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energy levels were found to be ?5.79/?3.80?eV for AF-T-INCN and???5.82/?3.79?eV for AT-T8-INCN, respectively. The organic solar cell devices fabricated with AF-T-INCN exhibited relatively low device performances with an open-circuit voltage (V OC) of 0.25?V, a short-circuit current density (J SC) 0.47?mA/cm2, a fill factor (FF) 29%, and power conversion efficiency (PCE) 0.03%, because of its strong aggregation in the blending condition. In contrast, AF-T8-INCN exhibited increased solubility and improved device performances with a high V OC of 1.24?V, a J SC 2.18?mA/cm2, a FF 28%, and PCE 0.76%.