Fig. 1. Surface morphology of pristine TiO₂ at the magnifications of (a) 1000× and (b) 40 000× showing macroscopic clusters and agglomerated particles respectively, (c, d) WO₃ coated TiO₂ nanoparticles layer showing randomly distributed TiO₂ nanoparticles and the porous nature.

Fig. 2. (Color online) (a–c) High resolution XPS scans showing Ti 2p, W 4f and O 1s peaks from the WO₃ coated TiO₂ sample. (d) XRD pattern obtained from the same sample.

Fig. 3. (Color online) Digital photographic images of (a) TiO₂ nanoparticle layer coated on FTO covered glass substrates showing the deposition of WO₃ surface passivation layer with different thickness values. (b) Photographs of the samples after N719 dye coating confirming the WO₃ did not affect the loading much. (c) UV–visible absorption spectra of the samples.

Fig. 4. (Color online) (a) J–V characteristics of the DSSC with and without WO₃ passivation on TiO₂. (b) Comparison of P_MAX of DSSCs, dark current characteristics of DSSCs in (c) linear and (d)semi-log scale showing the saturation current values.

Fig. 5. (Color online) Schematic illustration of (a) FTO/TiO₂/dye/electrolyte and (b) FTO/TiO₂/WO₃/Dye/electrolyte interfaces in DSSCs showing electron–hole transport and recombination mediated by defects in TiO₂.

Table 1. Photovoltaic parameters of the DSSCs measured under AM1.5 illumination level.