Enhancing the temporal stability of DSSCs with novel vinylpyrimidine anchoring and accepting group

Three compounds based on aniline, thiophene and vinylpyrimidine as anchoring group have been prepared and studied as light harvesting units for dye-sensitized solar cells (DSSCs). They comprise thiophenyl π-spacer systems with one or two thiophenes ( AT-Pyri, ATT-Pyri) and aniline as donor which is functionalized, in one case, with an hydroxyl group ( HO-AT-Pyri ). The bithiophene based dye ( ATT-Pyri ) shows higher extinction coefficients and smaller transition energy, as well as broader absorption spectrum. Thus, despite lower dye uptake, devices based on one thiophene and with the hydroxyl group ( HO-AT-Pyri ) have slightly higher power conversion efficiencies (η) as compared with the analogous dye without this group ( AT-Pyri ). However, the best performing device is based on the dye with bithiophene bridge ( ATT-Pyri) when a co-adsorbent is added to avoid the aggregation of the dye. The photovoltaic parameters of cells based on these vinylpyrimidine dyes are enhanced over 1000 h, especially for ATT-Pyri devices, which reach a η = 6,4%. • Sensitizers for DSSC based on vinylpyrimidine as novel anchoring and accepting group. • The hydroxyl group contributes to improving the adsorption of the HO-AT-Pyri dye on the TiO 2 surface. • Devices with a dye with a hydroxyl group HO-AT-Pyri enhance the photocurrent and photovoltage compared to AT-Pyri. • The ATT-Pyri dyes enhance the efficiency up to 1000 h after the device assembly.