Kiplang’at Michael Ng’eno^1,, Waweru Simon Mugo¹, Nelson Soitah Timonah¹

Dye-sensitized solar cells were fabricated using graphene on platinum-based counter electrodes, electrolyte and titanium dioxide thin films deposited on fluorine-doped tin oxide, FTO, using doctor-blade technique. The prepared CEs were characterized using UV-Vis spectrophotometer and four-point probe for optical transmittance and sheet resistance respectively. Transmittance of single and double layers graphene on platinum was noted to be high at visible wavelength. Each layer increase in graphene corresponds to decrease of 2.41% in the optical transmittance of graphene films. Sheet resistance was found to reduce with increase in number of graphene layers with 1150, 550 and 201 Ω/sq for monolayer, bi-layer and MLG on FTO respectively. The solar cell was then characterized by analyzing the photocurrent-voltage characteristics obtained through applying external bias on the solar cell and the results showed incorporation of graphene layers in platinum based CEs increase the short circuit current density and the photoelectric conversion efficiency (ƞ). However, incorporation of MLG on platinum based CE led to reduction of ƞ. Pt/single Layer-Gr, Pt/double Layer-Gr, Pt/multilayer graphene CE’s had a conversion efficiency of 3.42, 3.58 and 2.25 % respectively. Pt/double Layer-Gr based CEs showed the highest conversion efficiency and improvement of 6.87 % on ƞ as compared to that of reference platinum-based CEs.

graphene layers, sheet resistance, transmittance, Platinum/Gr counter electrode, DSSC