Perylenes as sensitizers in hybrid solar cells: how molecular size influences performance

Dye-sensitized solar cells (DSCs), one kind of hybrid solar cells, are being intensively developed due to their high efficiency and low cost. One of the main factors to improve the efficiency is the minimization of the recombination of holes and electrons at the TiO2/dye/electrolyte interface. To suppress the charge recombination, dye arrangement on the TiO2 surface plays the pivotal role in DSCs. Herein we report three perylene sensitizers of various molecular sizes, which are derived from the introduction of different groups in the 1,6-positions of the perylene core. The same donor (di-p-tert-octylphenylamino) and acceptor (anhydride) moieties in these perylene sensitizers render them highly similar spectroscopic and electrochemical properties, which can be used to compare the effect of the dye-loading on the TiO2 surface, namely, the photovoltaic performance as a function of the sensitizer size. These results will help in better understanding the complex relationship between the molecular size and the device performance.