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Multi-Edged Wrinkled Graphene like Carbon Wrapped Carbon Nanotubes and

Highly Conductive Pt Free Counter Electrode for Dye-Sensitized Solar Cells

Mridula Baro, Sundara Ramaprabhu*

Alternative Energy and Nanotechnology Laboratory, Department of Physics, Nano Functional Material Technology Centre, Indian Institute of Technology Madras, Chennai, India, 600036, *Phone: +91-44-22574862; fax: +91-44-22570509. *E-mail: [email protected]

Fig. S1 Representative FESEM images of the (a, b, c) surface and (d, e, f) cross section of the CEs coated with MWNTs, HEG and GWC based slurry on FTO glass with their typical photographs shown in the insets (a, b, c)

Synthesis of TiO2 mesoporous beads

At first, amorphous precursor TiO2 beads were synthesized using a sol-gel process. In a typical synthesis procedure,

5.296 g hexadecylamine (HDA) was dissolved in 800 ml ethanol and 0.1 M of 3.20 ml KCl solution was added. To this mixture solution, 17.6 ml titanium (IV) isopropoxide (TIP) was added under vigorous stirring at room temperature. The

1 resulting white TiO2 suspension was kept static for 18 h. Then TiO2 beads were collected using Millipore filter, washed with ethanol several times and dried in air at room temperature.

This as-prepared amorphous precursor TiO2 beads were converted to mesoporous TiO2 beads with a highly crystalline framework via solvothermal process. 1.6 g of the amorphous TiO2 beads was dispersed into a mixture of 20 ml ethanol and 10 ml deionized water followed by addition of 1 ml ammonia solution (25%). The mixtures were sealed in a 50 ml

Teflon-lined autoclave and kept at 160 °C for 16 h. The obtained product was collected by filtration, washed with ethanol, and dried at room temperature in air. The resultant powders were calcined at 500 °C for 2 h in air. This calcined TiO2 mesoporous powder was used to prepare of TiO2 paste for fabricating the TiO2 photoanode layer.

Figure S1 (a), (b) shows the highly porous TiO2 beads synthesized for the fabrication of TiO2 photoanode of the dye sensitized solar cell. Figure S1 (c) and (d) shows the front view and side view of the TiO2 film coated on the FTO. The

TiO2 film is around 15.83 µm asshown in the Figure S1 (d).

2 Fig. S2 FESEM images of (a), (b) TiO2 beads; (c) Front view (inset is the photograph of 0.36 cm TiO2 photoanode

2 film coated on the 1.25 ×1.66 cm FTO glass plate ) and (d) Side view of TiO2 photoanode film made from the slurry based on TiO2 beads

2 Fig. S3. Schematic of the DSSC fabrication