Flexible fluorine-doped tin oxide based composite electrodes for photovoltaic applications

G. Giusti, E. Puyoo, D.P. Langley, V. Consonni, D. Bellet
Laboratoire des Matériaux et du Génie Physique (LMGP), FR

Keywords: flexible substrate, spray pyrolysis, tin dioxide films, texture, transparent conductor


Fluorine-doped tin dioxide (FTO) thin films were deposited via ultrasonic spray pyrolysis directly on preheated polyimide (PI) - DuPont™ Kapton® polyimide flexible film substrates. All the FTO films deposited on PI substrates exhibited polycrystalline cassiterite structure and became more textured as the film thickness increased. A very similar observation was made recently by our group on FTO grown on glass substrates. Interestingly, the obtained FTO electro-optical properties were found already compatible with some flexible electronic applications. For example, FTO films deposited on PI at 400°C exhibited a low electrical resistivity of 7.7×10-4 Ω cm combined with a high total transmittance up to 80 % for wavelength larger than 780 nm. In addition, mechanical fatigue tests were performed to assess the stability of the thin film electrode under cyclic bending stress by measuring the electrical resistance versus the number of bending cycles thanks to an automated mechanical bench. The 215 nm thick film demonstrated a remarkable resistance to fatigue as compared with thicker films while keeping the above mentioned physical properties. Eventually, (composite) FTO layers incorporating ZnO nanoparticles for enhanced light trapping were fabricated and integrated into a working dye-sensitized solar cell.