Highly conjugated electron rich thiophene antennas on phenothiazine and phenoxazine-based sensitizers for dye sensitized solar cells

A series of organic dyes, CSORG6–CSORG9 were synthesized and successfully applied for dye-sensitized solar cells. All the dyes exhibited high open circuit voltage (VOC) compared to N719. Among all phenoxazine (CSORG7 and CSORG9) based sensitizers showed high PCE (η) of 6% under standard AM 1.5G solar irradiation. Under similar fabrication and evolution conditions N719 reached PCE (η) of 6.4%. •Diheteroanthracene based dyes were synthesized and used as sensitizer for DSSCs.•Phenoxazine (POZ) act as better electron donor compared to phenothiazine (PTZ).•All the dyes showed improved photovoltage compared to standard N719.•POZ dyes showed red shifted absorption with improved molar extinction coefficients.•Efficiencies of POZ based dyes reached 93% of the standard cell from N719. Four new organic dyes, coded as CSORG6, CSORG7, CSORG8 and CSORG9, comprising electron rich thiophene derivatives as antennas and cyanoacrylic acid as acceptor, bridged by phenothiazine or phenoxazine were designed and synthesized for dye-sensitized solar cells applications. They were fully characterized with their photophysical, electrochemical properties, density functional theory (DFT), time dependent density DFT (TDDFT) and the light-harvesting properties of the new sensitizers were evaluated with nanocrystalline TiO2-based devices. Among the four diheteroanthracene based dyes, phenoxazine (CSORG7 and CSORG9) based devices afforded the best photovoltaic performance (η) of 6% under standard AM 1.5G solar irradiation, whereas, N719 showed (η) 6.4% under the similar fabrication and evolution conditions.