A novel multilayered photoelectrode with nitrogen doped TiO2 for efficiency enhancement in dye sensitized solar cells

- Nitrogen doped TiO2 powder samples were synthesized by a modified wet chemical method.
- Highest efficiency of 8.00% was achieved by the cells made with N-doped TiO2 multilayer electrode.
- An identical multilayer electrode made with undoped TiO2 showed an efficiency of 4.22%.
- Optical absorption measurements show energy band gap narrowing due to N-doping.
- The enhancement in the efficiency is correlated with increased photocurrent density.

Nitrogen doped TiO2 powder samples were synthesized by a modified wet chemical method using aqueous ammonia and nitrogen gas purged on titanium tetra isopropoxide (TTIP). Photolectrodes with different combinations of layers of nitrogen − doped TiO2, undoped TiO2 and Degussa P25 TiO2 powders were used in dye sensitized solar cells (DSSCs). The highest conversion efficiency of 8.00% was achieved by the cells fabricated with compact layer/P25/N-doped TiO2 multilayer photoelectrode. This is an impressive enhancement in efficiency close to 89% with respect to a similar multilayer electrode made with undoped TiO2 which showed a conversion efficiency of 4.22%. The enhancement in the efficiency appears to be due to the increased photocurrent density of the DSSCs resulting mainly from energy band gap narrowing due to N-doping with some contribution from increased dye uptake by the novel multilayer electrode. These results have been substantiated by the reduced charge transfer resistance obtained from Electrochemical Impedance Spectra and the enhanced IPCE spectra of the DSSCs with N-doped TiO2 based multilayer electrode.

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