Exploring spray coating as a deposition technique for the fabrication of solution-processed solar cells

We investigate the characteristics of airbrush spray coated polymer solar cells based on a mixture of poly(3-hexyl thiophene) and (6,6)-phenyl C 61 -butyric acid methyl ester, deposited with different settings. We show smooth films yielding spray coated solar cells with power conversion efficiencies of 2.8%. In addition, we find that the spray coating technique allows the realization of polymer solar cells with a structural gradient in the vertical direction: the femtoliter scale droplets, distinctive of spray coating, dry very rapidly and subsequent layers can be deposited from the same solvent, without completely dissolving the underlying layers.