A new approach to the solvent system for inkjet-printed P3HT:PCBM solar cells and its use in devices with printed passive and active layers

Inkjet-printing is a suitable method to generate patterned structures from solvents containing active components. However, the process of inkjet-printing imposes severe limitations on the properties of the inkjet ink. This paper presents a new approach to solvent systems suitable for inkjet-printing common organic solar cell materials, poly(3-hexylthiophene) and 1-(3-methoxycarbonyl)propyl-1-phenyl[6,6]C61 as active layers in solar cells. Typically, low boiling point chlorinated solvents are used to dissolve P3HT and PCBM because both components are well soluble in these materials. During inkjet-printing, nozzle clogging due to evaporation of the ink in the inkjet print head is reduced when a high boiling point solvent is incorporated. Solar cells with active layers that were printed from an ink with a solvent system of chlorobenzene and trichlorobenzene showed power conversion efficiencies of 2.4% when active layer was dried at 130 °C. This compares to 2.6% for spin-coated solar cells from the same materials. In addition, devices with printed passive and printed active layers were prepared and power conversion efficiencies of 1.5% were achieved.