Design of Ethanol/Water-Processable Conjugated Polymers and Fullerene Derivatives for Eco-Friendly Processed Organic Transistors and Solar Cells*

It is very urgent to develop new electroactive materials that can be processed with eco-friendly solvents, because aromatic solvents is a big obstacle to transferring lab-scale to industry-scale production. In this work, we design highly-crystalline conjugated polymers and fullerene derivatives that can be processed with ethanol/water solvents for producing organic field effect transistors (OFETs) and organic solar cells (OSCs). Oligoethylene glycol (OEG)-based polar non-ionic side chains were attached to high-performing p-type conjugated polymers and n-type fullerene cores to provide solubility in ethanol/water mixtures. The introduction of flexible OEG chains induced lower T_m and T_c of conjugated polymer, which can improve processability of polymer into crystalline thin film. High-performance eco-OFETs and -OSCs yielding a hole mobility of 2.3 × 10^-2 cm² V^-1 s^-1 and a power conversion efficiency of 1.4% were demonstrated using ethanol/water solvent, which surprisingly outperformed the devices processed using toxic processing solvent.