Phenoxazine-based panchromatic organic sensitizers for dye-sensitized solar cells

• Three new dyes based on phenoxazine unit and indolinum carboxyl acid derivative were synthesized.
• All dyes exhibited panchromatic response both in CH2Cl2 solution and on TiO2 film.
• A best overall conversion efficiency of 5.1% was obtained for DSSCs with LJJ103.

A series of metal-free organic dyes LJJ101–LJJ103 composed of phenoxazine unit and indolinum carboxyl acid derivative have been synthesized for dye-sensitized solar cells. A systematic investigation has been conducted for the photology and electrochemistry properties of dyes LJJ101–LJJ103. Panchromatic spectra responses for all the three dyes have been obtained and extended to about 800 nm in near-infrared region. Compared to LJJ101, the introduction of thiophene and squaraine unit causes a red-shift absorption response for LJJ102 and LJJ103, respectively. When applied in dye-sensitized solar cells under AM 1.5 illumination, the device sensitized by LJJ103 yields the best conversion efficiency of 5.1% with a short-circuit photocurrent density of 13.7 mA/cm2, an open-circuit photovoltage of 502 mV and a fill factor of 74.0%.

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