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Objectives: To develop organic dye sensitized film electrodes from highly porous tin oxide (SnO 2 ) thin films prepared at room temperature using the SILAR technique. Methods/Analysis: SnO 2 films were fabricated by the successive ionic layer adsorption and reaction (SILAR) technique at room temperature and its sensitization was done using the organic dye Rose Bengal (RB). The effect of sensitization on the as-grown and annealed film electrodes was investigated. Findings: Crystalline films with cauliflower-like morphology exhibit a large inherent adsorptive surface area and exhibit steady transmittance of 60-80% in the visible region. As-grown SnO 2 films possess higher porosity and lower refractive index than that of the annealed films. SnO 2 films have a resistivity in the range of 10 -2 -10 -3 Ωcm. The dye adsorbed SnO 2 film electrodes have much higher absorbance and cover a broad visible region compared to the bare SnO 2 film electrodes. RB sensitization leads to an accelerated improvement in absorbed photon energy through the visible region of the spectrum extending from 2 to 3.75 eV. Novelty: Contrary to the sophisticated methods of preparation in the reported literature, highly porous crystalline SnO 2 thin films were prepared at room temperature, using glacial acetic acid and hydrogen peroxide by a cost-effective simple wet chemical method. Work demonstrates that SnO 2 films sensitized with RB act as an excellent dye-sensitized electrode, which can absorb almost half the visible spectrum (400-600 nm) of solar radiations. We believe that this is the unique report of surface modification of wet chemically prepared SnO 2 electrodes by the photo-sensitizer RB.

Objectives: To develop a unique wet chemical process for the rapid synthesis of SnO 2 thin films and hence to study the structural, morphological, optical and electrical properties of the films. Methods/Analysis: Polycrystalline SnO 2 thin films having a thickness in the range of 800-1000 nm with crystallite size less than 5 nm were synthesized within a time of 20 minutes and without the need of post-annealing using SILAR technique. Lattice parameters, c/a ratio, cell volume, dislocation density, refractive index, extinction coefficient and porosity of the SnO 2 thin films were determined. Findings: Films have a coarse and porous surface morphology with very fine pores distributed nearly uniformly on the film surface. The crystallite size and strain developed in the SnO 2 films were computed by the Williamson-Hall technique. Microstrain developed in the films is of the order of 10 -3 . SnO 2 films exhibit nearly 70% transmittance in the visible region. The optical band gap of the SnO 2 films is 3.65 eV. The refractive index of the films varies from 2.05 to 2.30 in the 450-1900 nm wavelength range. SnO 2 films exhibit a resistivity in the order of 10 -1 Ωcm. Novelty: Reports a unique rapid wet chemical process for the direct preparation of crystalline SnO 2 thin films using monoethaolamine at a temperature of 80 0 C. Literature survey reveals that no other method has yielded such type of good quality SnO 2 thin films at this temperature and without post annealing or sintering. First time crystalline SnO 2 films were prepared by a wet chemical process within 20 minutes.

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