First examples of pyran based colorants as sensitizing agents of p-type dye-sensitized solar cells

Three different pyran based dyes were synthesized and tested for the first time as photosensitizers of NiO based p-type dye-sensitized solar cells (p-DSSC). The molecules feature a similar molecular structure and are based on a pyran core that is functionalized with electron acceptor groups of different strength and is symmetrically coupled to phenothiazine donor branches. Optical properties of the dyes are deeply influenced by the nature of the electron-acceptor group, so that the overall absorption of the three dyes covers the most of the visible spectrum. The properties of devices based on the NiO electrodes sensitized with the investigated dyes were evaluated under simulated solar radiation: the larger short circuit current density exceeded 1 mA/cm2 and power conversion efficiency as high as 0.04% could be recorded. The performances of the fabricated p-DSSC have been compared to a reference cell sensitized with P1, a high level benchmark, which afforded a photoelectrochemical activity similar to the best example of our pyran sensitized devices (Jsc = 1.19 mA* cm−2 and η = 0.049%).