Planar, bulk and hybrid merocyanine/C60 heterojunction devices: a case study on thin film morphology and photovoltaic performance

Abstract

The growth of a thermally deposited merocyanine (HB364) thin film can be modified through insertion of a transition metal oxide layer between an indium tin oxide (ITO) covered glass substrate and the dye film. Pure or V₂O₅ modified ITO substrates result in highly crystalline HB364 films where the dye molecules adopt an edge-on orientation. Changing the transition metal oxide layer to WO₃ or MoO₃ results in a less ordered dye film with a mixed growth of edge-on and face-on orientations. Planar HB364/C₆₀ heterojunction (PHJ) solar cells are fabricated using the different transition metal oxides as the anode buffer layers. The devices with a pure ITO or a V₂O₅ modified anode demonstrate the highest power conversion efficiencies up to 2.7% that also outperform HB364:C₆₀ bulk heterojunction (BHJ) devices (2.5%). Finally, HB364/HB364:C₆₀ hybrid heterojunction (HHJ) cells are fabricated showing the highest power conversion efficiency of 2.9%.