Complex electrochemical study of reduced graphene oxide/Pt produced by Nd:YAG pulsed laser reduction as photo-anode in polymer solar cells

In the present study, reduced graphene oxide/platinum (rGO/Pt) nanocomposites were synthesized using Nd:YAG pulsed laser, and applied as photo-anode materials in normal architecture P3HT-based bulk heterojunction polymer solar cells (BHJ PSCs). XRD and TEM analysis confirmed the successful simultaneous reduction of GO and Pt ions to rGO and Pt nanoparticles (NPs) with sizes less than 20 nm by laser irradiation. The influences of the solvent type used in the laser production of rGO/Pt were investigated to achieve more appropriate photo-anode material in terms of surface morphology, electrical conductivity and charge transfer resistance. The flat-band potential (V-bi) of the rGO/Pt-based photo-anodes was adjusted by altering the weight percentage of Pt nanoparticles (NPs) loaded onto rGO nanosheets. Several physical and electrochemical characterization techniques were used to follow the influences of Pt NPs content on the sheet resistance (R-sh), optical transparency, charge carrier mobility, charge transfer resistance, and V-bi of the prepared photo-anodes. The R-sh decreased significantly by increasing the Pt NP wt%, while this was accompanied by negligible decreases in the transparency of photo-anodes comprising up to 10 wt% Pt NPs. Desirable stability and good adhesion of the synthesized materials on the glass substrate were proved using cyclic voltammetry, SEM and TEM images. Sequential increase of Pt NPs wt% from1 to 10 wt% resulted to a considerable decrease in the series resistance of PSCs, in which PSC prepared based on rGO/Pt-based photo-anode containing 10 wt% Pt NPs showed the lowest series resistance of 8 Omega/cm(2), and considerably higher PCE (similar to 800%) compared to PSC prepared based on rGO. Higher Pt loading (>10 wt%) on rGO led to the increase of rGO/Pt surface roughness, a considerable decrease of optical transparency of the corresponding photo-anodes, and the attenuation of the photovoltaic parameters of the corresponding PSCs.