Embedded chromium current collectors for efficient and stable large area dye sensitized solar cells

Abstract

New route for fabrication of transparent conducting glasses for efficient photocurrent collection in large area DSSCs is demonstrated: current collectors were formed beneath the glass surface to achieve high cross-sectional area and good conductivity. The advantages of chromium metal for current collectors in DSSCs are presented. Polarization measurements revealed passivity of Cr in back electron recombination with electrolyte. Chromium was electrodeposited ca. 20 mu m beneath glass surface into grooves in FTO-glass, which had been formed by photolithography assisted wet etching. Robust adhesion of Cr to glass up to 500 degrees C was achieved using interlayer of titanium, controllable formation of sponge-like microstructure of the metal and by designing wave-shape conducting lines. DSSCs photoanodes of 2.5 x 2.5 and 6.5 x 6.5 cm(2) were assembled on Cr-embedded FTO-glasses. The resulting DSSCs show power conversion efficiencies of 5.3% and 3.6% respectively for the 6.3 and 42.3 cm(2) devices; it outperforms the cells with blank FTO substrates, respectively 2.6 and 0.4% of efficiency, mainly due to the improvement of the filling factors. Significant decrease of series and electron transfer resistances in the photoanodes assembled on Cr-embedded FTO glasses was revealed. The cells with Cr current collectors maintained their efficiency during 3000 h under natural ageing.