Organic dyes efficiently utilizing low-energy photons in the near-infrared (NIR) region are desperately needed in dye-sensitized solar cell (DSC) devices. Thieno[3,4-b]pyrazine (TPz) was examined as an electron deficient π-bridge enabling NIR spectral access in DSCs. Three new TPz based dyes (NL11-NL13) were synthesized and power conversion efficiencies up to 8.1 % was achieved. This study reveals it is imperative to precisely control the exited-state energies of dyes to extend solar-to-electric conversion into the NIR region for DSCs. TPz dye energetics were tuned through a careful selection of strong donor substituents. Additionally, donor size influence versus dye loading on TiO2 surface was evaluated with respect to the TiO2 surface protection designed to prevent recombination of electrons. Importantly the dyes in this series were demonstrated to work with low Li+1 loading with both iodine and cobalt redox shuttle systems. Co-sensitization with a visible light absorbing dye, D35, produced devices with incident photon-to-current conversion efficiencies reaching 800 nm and a photocurrent density of 17.6 mA/cm2. This is one of the highest current densities known for an organic dye based DSC device.

Effect of donor strength and bulk on thieno [3,4-b]pyrazine-based panchromatic dyes in dye-sensitized solar cells

255th National Meeting (2018)

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