Highly Efficient Non-Fullerene Organic Photovoltaics Processed from o-Xylene without Using Additives

Most efficient organic photovoltaic (OPV) devices are fabricated using halogenated solvents, which are hazardous and-environmentally unfriendly. From an industrial perspective, green solvents are necessary for the roll-to-roll production of OPV modules. In this study, we fabricated nonfullerene (NF) OPV devices that are based on the blend films of PTB7-Th and 3,9-bis(2-methylene-(3-(1,1-dicyanomethylene)-indanone)-5,5,11,11-tetrakis(4-hexylpheny1)-dithieno [2,3:2',3'-d']-s-indaceno[1,2-b:5,6-b'-dithiophene (ITIC) by using o-xylene and tetrahydrofuran (THF) as the processing solvents and chlorobenzene (CB) and o-dichlorobenzene as the control solvents. We compared the variations in the ultraviolet visible absorption, atomic force microscopy-derived phase morphologies, space-charge-limited current carrier mobilities, and power conversion efficiency (PCE) of the related OPV devices. The high solubility of ITIC and PTB7-Th in the solvents yielded PCE of 8.11% and 6.79% for the o-xylene- and THF-derived devices, respectively. The PCE of 8.11% is among the highest performance reported to date for NF OPV devices fabricated using a green solvent (without additives or post-treatment). Furthermore, this PCE was suppressed in the CB-based device (PCE: 7.41%) because of the clearly defined morphology and higher and balanced carrier mobility.