Photovoltaic performance of plasmonic thin films with different structure of Au and TiO2

Abstract

Metal-oxide nanostructures with Surface Plasmon Resonance (SPR) have been introduced to improve the light absorption ability of dye sensitized solar cells (DSSCs) so that the energy conversion efficiency can be enhanced. It should be noted that the structure of metal nanoparticles and the oxide substrate greatly influence the performance of the solar cells, both to utilize SPR to the fullest and to overcome the drawbacks such as charge recombination involved with metal nanoparticles. We studied the morphology of spin-coated thin films with different structures of Au and TiO2, FTO/TiO2/Au NPs, FTO/Au NPs/TiO2 and FTO/TiO2/Au/TiO2 and examined the surface plasmon resonance effect on the light absorption ability and energy conversion behavior of dye sensitized solar cells with the as fabricated thin films as photo anodes. Electrode with Au NPs loaded on the top of TiO2 thin film showed improved optical absorption in the visible region compared to the control sample of TiO2 due to the surface plasmon resonance of Au NPs. However, the dye sensitized TiO2-Au NPs films showed decreased photocurrent under illumination due to the charge recombination caused by bare Au NPs. On the other hand, when Au NPS were loaded beneath the TiO2 film, the plasmonic electrode exhibited a 37% enhancement and increased incident photon-to-photocurrent efficiency (IPCE) in consistent with the improvement in absorption spectrum. To further confirm the role of Au NPs in the plasmonic films, the sandwich-like structure of TiO2-Au-TiO2 was introduced, behaving improved photovoltaic performance compared to the control TiO2 electrode. Such results reveal that the design of structure can be of great importance to identify the favorably enhanced direction of plasmonic structure resulting from plasmonic scattering to trap light which confines light within the active TiO2 layer to promote DSSCs. Dipole Discrete Approximation (DDA) simulation feedback supported the experimental results. This concept is applicable to potential plasmonic devices for DSSCs.