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ITO-free organic solar cells with roll-to-roll coated organic functional layers from non-halogenated solvents

: Kaduwal, D.; Schleiermacher, H.-F.; Schulz-Gericke, J.; Kroyer, T.; Zimmermann, B.; Würfel, U.


Solar energy materials and solar cells 124 (2014), S.92-97
ISSN: 0927-0248
Fraunhofer ISE ()
Solarzellen - Entwicklung und Charakterisierung; Alternative Photovoltaik-Technologien; Farbstoff- und Organische Solarzellen; Grid; Flexible; ITO-free; sputtering; Coating

This work reports on indium tin oxide (ITO)-free organic solar cells with roll to roll (R2R) processed organic functional layers. The device stack comprises a chromium–aluminum–chromium (Cr–Al–Cr) electron contact layer on a polyethylene terephthalate (PET) film, a photoactive layer of poly(3-hexylthiophene) (P3HT): (6,6)-phenyl C61 butyric acid methyl ester (PCBM), a hole transport layer of Poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate) (PEDOT:PSS) and a silver (Ag) grid for current collection. For the photoactive layer the non-halogenated solvent o-Xylene was used in order to reduce the impact on health and environment for R2R coating on ambient atmospheric conditions. The Cr–Al–Cr layers were sputtered onto the PET rolls in a batch process while the photoactive layer as well as the hole transport layer were applied in a continuous R2R process by slot die coating. The Ag grid was either thermally evaporated through a shadow mask as reference process or deposited by aerosol printing as a more production compatible process. Device efficiencies up to 2.9% on an active area of 1.1 cm2 were obtained with no difference for the method of grid processing. These experimental results demonstrate that R2R coated organic functional layers in ITO-free devices obtain the same device performance as compared to spin coated laboratory cells.