Acid@base co-sensitization strategy for highly efficient dye-sensitized solar cells

Abstract Two new base dyes bearing pyridyl acceptor (Py-1 and Py-2) are synthesized, which are respectively co-sensitized with an acid dye containing cyanoacetic acceptor (NP-1), constructing the acid@base co-sensitized solar cells (co-DSSCs). The lightspot is that the carboxylic and pyridyl groups could anchor onto the Bronsted-acid and Lewis-acid sites of TiO2 surfaces, respectively. The research results show that the combination of these acid and base dyes is beneficial to suppress the competitive adsorption between dyes, thus increasing the dye coverage on TiO2 surfaces and decreasing the electron recombination, and further raising the photovoltage; moreover, their complementary spectral responses can significantly increase the photocurrent. Therefore, the acid@base co-DSSC based on NP-1@Py-2(2:3) delivers the best photovoltaic performances in comparison to the DSSC based on NP-1, in which the photovoltaic efficiency is increased by 32.5% (from 4.0% to 5.3%). Furthermore, the photovoltaic performances under different irradiation and long-term stability measurements can provide a basis for application evaluation of co-DSSCs.