Enhanced photovoltaic performances of dye-sensitized solar cells sensitized with D-D-π-A phenothiazine-based dyes

•Two new PTZ-based organic dyes were synthesized and characterized.•The dyes are studied by DFT and TD-DFT calculations.•The introduction of benzil-based auxiliary donors improves the light-harvesting ability.•The DSSCs based on WY5 and WY6 have higher Jsc than that of T0.•The DSSC based on dye WY6 obtains the highest η of 5.52%.

Two new D-D-π-A phenothiazine-based metal free organic dyes (WY5, WY6) were designed, synthesized, and applied in dye-sensitized solar cells (DSSCs) by introducing of benzil-based auxiliary electron donors into simple D-π-A phenothiazine dye to improve the related photovoltaic performances. In the WY6-based solar cell, 4,4′-dimethoxybenzil acts as electron donor was used to improve the electron donating ability. So, the WY6-based solar cell finally obtains a better photovoltaic performance than that of WY5-based one. Furthermore, with the addition of benzil-based auxiliary donor, the absorption properties turn better, which directly results in the enhanced short-circuit photocurrent density (from 8.78 (T0) to 10.58 (WY5) and 11.50 mA cm−2 (WY6)) and thus the enhanced power conversion efficiency (from 4.24 (T0) to 4.78 (WY5) and 5.52% (WY6)). In a word, the addition of benzil-based auxiliary electron donors effectively improved the performances of DSSCs.

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