Organic photo-sensitizers were designed and synthesized based on a phenothiazine framework containing single- and double-electron acceptors that were bridged with thiophene for the dye sensitized solar cells (DSSCs). The optimized geometries were determined with density functional theory (DFT) calculations to estimate the photovoltaic properties of the dyes in the design stage. The organic dye with the double electron acceptors exhibited a better light absorption at long wavelength and an effective electron extraction pathway from the electron donor to the TiO2 surface, leading to an improved short-circuit current (11.6 mA cm-2), compared with that of the dye with the single electron acceptor (10.2 mA cm-2) and the conventional N3 Ru-dye (10.4 mA cm-2). Contrarily, the open-circuit voltage of the organic dye with the double electron acceptors decreased because the additional protonated carboxylic groups caused a positive shift in the Fermi level of TiO2.
Bibliographical noteFunding Information:
This research was supported by Basic Science Research Program through the National Research Foundation of Korea(NRF) funded by the Ministry of Education, Science and Technology(2010-0017088), and by the Ministry of Education, Science Technology (MEST) and National Research Foundation of Korea(NRF) through the Human Resource Training Project for Regional Innovation.
- Dye-sensitized solar cells
- Multi-anchoring groups
- Organic dyes
- Short-circuit current enhancement
- Structure optimization
- Thiophene bridge