Enhanced photovoltaic performance of semiconductor-sensitized ZnO-CdS coupled with graphene oxide as a novel photoactive material.

We report, for the first time, a ternary hybrid composite of ZnO, CdS, and graphene oxide (GO) as a one-coat paintable solution in performing the role of a photoanode for the semiconductor-sensitized solar cell, wherein hierarchical ZnO-CdS heteroarrays are embedded onto the GO sheets. The photoconversion properties of the hybrid ternary-system-based photoanodes are evaluated in the photovoltaic devices having Pt and Ag as the counter electrodes with sulfide/polysulfide redox couple as the electrolyte. Power conversion efficiency (PCE) of ~2.82% has been achieved with a short-circuit current density (Jsc) of ~7.3 mA/cm(2), a maximum open-circuit voltage (Voc) of 703 mV, and a fill factor (FF) of 54% for the photovoltaic cell with Pt as a counter electrode. The identical hybrid photoanode against the Ag counter electrode resulted in the following values: PCE ≈ 1.96%, Jsc ≈ 5.7 mA/cm(2), Voc ≈ 565 mV, and 63% FF. The band position proximity of CdS, ZnO, and GO in the proposed ternary system facilitates an efficient electronic interactions thereby promoting the electron transport within CdS-ZnO-GO. The hierarchically grown CdS nanorods over ZnO nanoparticle act as the sensitizer for ZnO, enhancing the visible light harvesting ability. The loading of 1.0 wt% of GO to ZnO-CdS results in enhanced separation of photogenerated electrons and holes within the photoactive layer, thereby improving the photovoltaic performance. The electronic interactions of GO to ZnO-CdS is evident from the drastic quenching of fluorescence, reduced exciton lifetime and Raman scattering measurements. In order to study the effect of GO in the photovoltaic performance, we have compared our result with the photoelectrical parameters of the devices fabricated using the binary ZnO-CdS composite as GO-free photoanodes.