• G K R SENADEERA

      Articles written in Bulletin of Materials Science

    • Efficiency enhancement in dye-sensitized solar cells with co-sensitized, triple layered photoanode by enhanced light scattering and spectral responses

      G K R SENADEERA D BALASUNDARAM M A K L DISSANAYAKE B A KARUNARATNE A M J S WEERASINGHE C A THOTAWATTHAGE T JASEETHARAN J M K W KUMARI D L N JAYATHILAKA

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      A method for impressive efficiency enhancement in TiO$_2$-based nanoparticle (NP) dye-sensitized solar cells (DSSCs) is demonstrated by using a co-sensitized triple layered photoanode, comprising a nanofibre (NF) layer of TiO$_2$ sandwiched between two TiO$_2$ P25 NP layers. Rose Bengal (RB) and Eosin-Y (EY) dyes are used for the co-sensitization. DSSCs with conventional TiO$_2$ (P25) NP bi-layer photoanode (NP/NP), sensitized with EY, showed an overall power conversion efficiency (${\eta}$) of 0.89% under the illumination of 100 mW cm$^{–2}$ (AM 1.5) with iodide-based liquid electrolyte. Whereas DSSCs fabricated with triple layered photoanode (NP/NF/NP) with the same total thickness and sensitized with EY yielded 1.77% efficiency under the same illumination conditions, showing an impressive ${\sim}$99% enhancement in the overall power conversion efficiency. The DSSCs fabricated with RB-sensitized NP/NP and NP/NF/NP photoanodes showed 0.25 and 0.73% efficiencies, respectively. Upon optimization, DSSCs fabricated with co-sensitized NP/NP bilayer and NP/NF/NP triple layer photoanodes showed 1.04 and 2.09% efficiencies, respectively, showing again an impressive ${\sim}$100% enhancement in ${\eta}$ due to the co-sensitized triple layer photoanode structure. Increase in the short circuit photocurrent density, UV–visible absorptions measurements, incident photon to current efficiency and electrochemical impedance spectroscopic measurements confirmed that this enhancement is very likely due to the enhanced light harvesting and reduction of recombination of photoelectrons combined with the enhanced spectral responses of the cosensitized triple layered photoanode.

    • Influence of citric acid linker molecule on photovoltaic performance of CdS quantum dots-sensitized TiO$_2$ solar cells

      G K R SENADEERA W I SANDAMALI M A K L DISSANAYAKE T JASEETHARAN V P S PERERA C N RAJENDRA N KARTHIKEYAN LAHIRU A WIJENAYAKA

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      Influence of citric acid on the photovoltaic properties of the CdS quantum dot-sensitized TiO$_2$ solar cells (QDSSCs) was studied. Tethering of citric acid molecules with both TiO$_2$ and CdS quantum dots (QDs) was confirmed by Fourier transform infrared spectroscopy technique. High-resolution transmission electron microscopic studies revealed that QDs with average size of ${\sim}$4.5 nm, were tethered with TiO$_2$ nanoparticles of diameter ${\sim}$40 nm. Presence of Cd, S,C, Ti and O elements in the composite photoanode and their uniform distribution throughout the photoanode were confirmed by energy dispersive X-ray spectroscopy measurements. QDSSCs fabricated with pristine TiO$_2$ photoanode exhibited a short circuit current density ($J_{SC}$) of 5.80 mA cm$^{-2}$ and an overall power conversion efficiency (${\eta}$) of 1.10%, whereas solar cells made with citric acid-treated, photoanode-exhibited a $J_{SC}$ of 8.20 mA cm$^{-2}$ with 1.50% efficiency under 100 mW cm$^{-2}$ (AM 1.5) light illumination. This is an impressive 60% increase in the $J_{SC}$ and ${\sim}$36% enhancement in the overall power conversion efficiency. Interfacial resistance of QDSSCs is estimated by using electrochemical impedance spectroscopy revealed that citric acid treatment enhanced both the electron injection to the conduction band of the TiO$_2$ from the CdS as well as the overall charge transfer of the device, while decreasing the recombination of the photo-generated electrons with their holes in the electrolyte.

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