D-π-A Type Phenothiazine Organic Dyes for Dye-Sensitized TiO2 Solar Cells

Here, two phenothiazine (PTA) based D-pi-A organic dyes (TC6PTA and TEC6PTA) were prepared. Their optical, excitonic and electrochemical properties were investigated and their practical application in dye-sensitized solar cells (DSCs) was also demonstrated. The PTA bridge EDOT pi-conjugated moiety contributed to the broad absorption and low-energy lambda(max) of the UV/VIS spectra, resulting in a small energy gap. Comparison showed TEC6PTA to have a higher absorption coefficient and smaller optical bandgap than TC6PTA. However, the power conversion efficiency (PCE) of the TC6PTA based DSC was 7.55% (TEC6PTA was 4.79%), higher than that of the N719 based DSC. Femtosecond time-resolved photoluminescence data show the electron injection at the TC6PTA/TiO2 interface to be more efficient than that at the TEC6PTA/TiO2 interface, which explains the higher PCE of the TC6PTA based device, including both the higher open-circuit voltage (V-OC) and short-circuit current (J(SC)).