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ZnO Thin Films with Adjusted Surface Work Function for Organic Solar Cells
S. Wiesner, V. Hinrichs, A. Steigert, D. Greiner, W. Ludwig, I. Lauermann, M.I. Rusu, M.C. Lux-Steiner
ITO, Organic Solar Cell, PEDOT:PSS, ZnO:Al, DMAE
Thin Film Solar Cells
Subtopic: Organic-based PV
Event: 27th European Photovoltaic Solar Energy Conference and Exhibition
Session: 3DV.4.59
2945 - 2947
ISBN: 3-936338-28-0
Paper DOI: 10.4229/27thEUPVSEC2012-3DV.4.59
0,00 EUR
Document(s): paper


An ITO/PEDOT:PSS (poly(3,4-ethylendioxythiophene)-poly(styrenesulfonate)) electrode is widely used as anode in organic solar cells (OSCs). Aluminium doped zinc oxide (ZnO:Al) is presented as a possible substitution for ITO in such anodes. Containing only abundant elements, ZnO:Al serves as cost effective alternative to the indium requiring ITO. To optimize the surface work function of the ZnO:Al/ PEDOT:PSS anode the pH value of the PEDOT:PSS dispersion is modified. In this work 2-dimethylaminoethanol (DMAE) is used for the pH-modification of the PEDOT:PSS dispersion. PEDOT:PSS dispersions modified by different DMAE concentrations were applied to both ITO and ZnO:Al films. The surface work functions of the prepared electrode stacks were determined by ultraviolet photoelectron spectroscopy (UPS) and related to the corresponding pH value. Additionally, we investigated the influence of the modified PEDOT:PSS layers on the photovoltaic properties in ZnPc:C60 based organic solar cells using ITO as well as ZnO:Al as TCO. By analysis of the solar cell performance of ZnO:Al based devices we identified a range of the DMAE concentrations showing the highest device efficiency. In this range we observed a solar cell performance similar to that of solar cells with ITO as TCO. Comparison of the open circuit voltage and the surface work function shows that a minimum work function of ~ 4.7 eV is necessary to form a charge selective contact at the anode/absorber interface.