Antti Ojala

Parallel Bulk‐Heterojunction Solar Cell by Electrostatically Driven Phase Separation

Thermal co-evaporation of C(60) fullerene and two merocyanine dyes affords bulk heterojunction solar cells with improved short-circuit currents and power conversion efficiencies in comparison with the respective single donor cells. These results are rationalized by the formation of three distinct subphases driven by differences in molecular shape and electrostatic interactions.

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

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%.