Dresden 2017 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 57: Organic Photovoltaics and Electronics II (joined session with CPP)

HL 57.6: Talk

Wednesday, March 22, 2017, 16:30–16:45, POT 81

Semitransparent Electrodes for Evaporated Small Molecule Organic Solar Cells — •Dhriti Sundar Ghosh and Karl Leo — Dresden Integrated Center for Applied Physics and Photonic Materials (IAPP), TU Dresden

Transparent Electrodes are key in novel flexible devices. We report a highly efficient microcavity assisted small molecule organic solar cell (SM-OSC), containing an indium-free semitransparent TiO2(30nm)/Ag 9nm based transparent electrode with average visible transmittance of 66.7% and sheet resistance of 6.3 Ohm/sq. The electrode also consisted of a wetting layer of polyethyleneimine which promotes the growth of ultrasmooth, and highly conductive Ag films even at very low thicknesses. The role of high index TiO2 undercoat layer is investigated in detail by optical simulations and is shown to enhance the microcavity effect, leading to increased light coupling into the photoactive layer. With comparable photocurrent, and high fill-factor values owing to much better electrical properties, the semitransparent electrode based SM-OSC outperforms the state-of-art indium tin oxide (ITO) based reference device with photon conversion efficiency of 8.1% compared to 7.7% despite having lower transmittance (~21%) relative to ITO. This work demonstrates that a properly designed semitransparent TE is a promising alternative to ITO and can lead to more efficient photovoltaic devices.