Combining Energy Conversion and Storage: A Solar Powered Supercapacitor

• A plasmonic TiO2/CdS/Au fibers photoanode is fabricated for the first time.
• The efficiency of the plasmonic cell is greater by 1.35 times than the non-plasmonic one.
• A solar powered supercapacitor is developed with plasmonic photoanode and multiwalled carbon nanotubes.
• The solar cell current charges the supercapacitor.
• A specific capacitance of 150 F g−1 is achieved under sunlight without any external bias.

A solar powered supercapacitor wherein a plasmonic quantum dot solar cell (QDSC) sources the photocurrent for charging/discharging a conjoined supercapacitor based on multiwalled carbon nanotubes (MWCNTs) is demonstrated. Gold or Au fibers are integrated into a titanium dioxide/cadmium sulfide (TiO2/CdS) electrode to yield a TiO2/CdS/Au photoanode. The plasmonic effect of Au fibers is reflected in the higher incident photon to current conversion efficiency (IPCE = 55%) and an improved overall power conversion efficiency (3.45%) produced by the TiO2/CdS/Au photoanode relative to the non-plasmonic TiO2/CdS photoanode. A Janus type bi-functional electrode composed of MWCNTs on either face separated by glass is prepared and it is coupled with the TiO2/CdS/Au electrode and another MWCNT electrode to yield the tandem solar powered supercapacitor. By channelling the photocurrent produced by the QDSC part, under 0.1 sun illumination, the capacitance of the symmetric supercapacitor, without the application of any external bias is 150 F g−1 which compares well with reported values of electrically powered MWCNT supercapacitors. Our innovative design for a photo-supercapacitor offers a new paradigm for combining low cost photovoltaics with energy storage to yield a technologically useful device that needs nothing else other than solar energy to run.

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