Organic sensitizers incorporating 3,4-ethylenedioxythiophene as the conjugated bridge: Joint photophysical and electrochemical analysis of photovoltaic performance

• 3,4-Ethylenedioxythiophene was introduced as the conjugated bridge in organic sensitizers.
• Light-harvesting ability was enhanced with a notable increase in Jsc.
• Joint photophysical and electrochemical analysis of conjugated bridge on photovoltaic performances.
• The driving force of ∼150 mV is workable for the indoline-based dye regeneration process, resulting in an overall efficiency of 6.05%.

Two novel D–π–A organic dyes containing either an indoline donor or a triphenylamine donor with each containing the 3,4-ethylenedioxythiophene unit as the conjugated bridge, were developed for dye-sensitized solar cells. Incorporating 3,4-ethylenedioxythiophene as the conjugated bridge brings several characteristics, such as broadening absorption range and increasing molar extinction coefficients, and improving electron injection with enhancement of the short-circuit photocurrent. The indoline containing dye shows a more negative oxidation potential and a bathochromic shift in absorption spectra than the triphenylamine substituted dye, indicative of the more powerful electron-donating capability of the indoline unit. With coadsorption of chenodeoxycholic acid, the indoline dye based dye-sensitized solar cell exhibited promising conversion efficiency of 6.05%, with a short-circuit photocurrent of 13.23 mA cm−2, open circuit voltage of 642 mV, and a fill factor of 0.711. In the indoline dye system, the dye-sensitized solar cell is workable with the driving force of 150 mV for the dye regeneration process, paving a road toward minimizing energy losses in the dye regeneration process.