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

Abstract

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-hexylphenyl)-dithieno[2,3-d: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.