A new method for fabricating micropatterns of MEH-PPV thin films with surface roughnesses below 1nm is proposed, using electrospray deposition and a dual-solvent technique. The basic concept is that nanoparticles are deposited on the target substrate just before they become completely dry, by adding a solvent that has an evaporation speed relatively lower than that of the original solution.

A high‐efficiency bulk heterojunction organic photovoltaic cell (OPV) was achieved by the electrospray deposition method. The surface roughness of the P3HT:PCBM thin film can be reduced using the mixed solvent consisting of o‐dichlorobenzene (o‐DCB) and acetone. The effect of acetone concentration is related to its dielectric constant. Under an optimized concentration of acetone in o‐DCB (20 vol%), the P3HT/PCBM active layer with a smooth surface can be formed, and the power conversion efficiency of the OPV was 1.9%.magnified image(© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

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