Tunable photovoltaic performance of preferentially oriented rutile TiO2 nanorod photoanode based dye sensitized solar cells with quasi-state electrolyte

Abstract

Photoanodes made of highly oriented TiO2 nanorod (NR) arrays with different aspect ratios were synthesized via a one-step hydrothermal technique. Preferentially oriented single crystalline rutile TiO2 was confirmed by the single peak in an XRD pattern (2θ = 63°, (0 0 2)). FESEM images evidenced the growth of an array of NRss having different geometries with respect to reaction time and solution refreshment rate. The length, diameter and aspect ratio of the NRs increased with reaction time as 4 h (1.98 μm, 121 nm, 15.32), 8 h (4 μm, 185 nm, 22.70), 12 h (5.6 μm, 242 nm, 27.24) and 16 h (8 μm, 254 nm, 38.02), respectively. Unlike a conventional dye-sensitized solar cell (DSSC) with a liquid electrolyte, DSSCs were fabricated here using one-dimensional rutile TiO2 NR based photoanodes, N719 dye and a quasi-state electrolyte. The charge transport properties were investigated using current–voltage curves and fitted using the one-diode model. Interestingly the photovoltaic performance of the DSSCs increased exponentially with the length of the NR and was attributed to a higher surface to volume ratio, more dye anchoring, and channelized electron transport. The higher photovoltaic performance (Jsc = 5.99 mA cm−2, Voc = 750 mV, η = 3.08%) was observed with photoanodes (16 h) made with the longer, densely packed TiO2 NRs (8 μm, 254 nm).