Dresden 2009 – scientific programme

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 26: Organic Photovoltaics I

CPP 26.8: Talk

Wednesday, March 25, 2009, 15:45–16:00, ZEU 222

Inverted Bulk Heterojunction Solar Cells — •Sofie Khalil and Klaus Meerholz — University of Cologne, Institute for Physical Chemistry, Luxemburger Str. 116, 50969 Cologne, Germany

Solution processed polymer photovoltaics are nowadays a very promising low-cost fabrication technology for renewable energy sources. Nevertheless research made onto bulk heterojunction (BHJ) with structure: ITO/ PEDOT:PSS/ blends of regioregular poly-3-hexylthiophene (RR-P3HT) and the fullerene derivative [6,6]-phenyl C61 butyric acid methyl ester (PCBM) / Ca:Ag showed inherent lifetime limitations due the use of PEDOT:PSS and low work-function metal electrode. In this talk we will show an alternative device with a new stacking order of layers: the inverted solar cells. In these devices to avoid the air sensitive and lifetime limiting materials we use a stable transparent anode electrode with lower energy level than the stable high-work function metal top electrode. The direction of the carrier flow is therefore inverted due to the inversion of the direction of the internal field. Inverted bulk-heterojunction solar cell made RR P3HT and PCBM as the active layer in the structure: ITO / TiOx / RR-P3HT-PCBM / metal electrode were studied. The transparent TiOx acts as electron-collecting electrode and the metal electrode as hole-collecting electrode. Different parameters have been investigated: thickness and treatment of the TiOx layer, solvent, thickness of the active layer, molecular weight of the polymer, post-annealing process, work-function of the metal electrode. And then a comparison of lifetime between a regular solar cell and an inverted one will be presented.