High-performance organic solar cells based on a low-bandgap poly-thienothiophene-benzodithiophene polymer and fullerene composite prepared by using the airbrush spray-coating technique

In the present work, we have demonstrated high-performance organic solar cells with spray coated active layers. The influence of the nanomorphology on the power conversion efficiency of poly[[4,8-bis[(2-ethylhexyl)oxy]benzo[1,2-b:4,5-b′]dithiophene-2,6-diyl] [3-fluoro-2-[(2-ethylhexyl)carbonyl] thieno[3,4-b]thiophenediyl]] (PTB7):[6,6]-phenyl-C71-butyric acid (PC71BM) methyl ester bulk heterojunction solar cells is presented. Active layers were prepared using a chlorobenzene solvent containing a small volume of 1,8-diiodooctane as an additive by spray coating with conventional handheld airbrushes. The surface morphology of the active layers deposited for various spray-coating times was examined using atomic force microscopy. The resulting devices were measured under AM 1.5G (100 mW/cm2) conditions in an ambient atmosphere. The optimized spray-coated PTB7:PC71BM film showed a high solar cell performance with a short-circuit current density of 14.20 ± 0.41 mA/cm2, a fill factor of 56.00 ± 0.02% and a power conversion efficiency of 5.96 ± 0.15%.