Understanding the Role of Electron Donor in Truxene Dye Sensitized Solar Cells with Cobalt Electrolytes

To understand the role of electron donor in organic dye sensitized solar cells employing cobalt electrolytes, two new organic dyes (M41 and M42) and a reference dye (M29) have been synthesized. We investigated the effects of the electron-withdrawing/electron-rich group in the electron donor on the photophysical and electrochemical properties of these dyes. In addition, the electron transfer kinetics of devices were compared by using two cobalt electrolytes (Co(II/III)-phen and Co(II/III)-Clphen) with different oxidation potentials. Regardless of the electrolyte selection, M42 shows a higher efficiency in comparison with those of M41 and M29. M42 in combination with the Co(II/III)-phen redox couples yielded an efficiency of 9.69% under the standard light illumination (AM 1.5G, 100 mW cm(-2)). We also evaluate the influence of light harvesting capacity, regeneration force of oxidized dyes, and charge recombination on the performance of studied DSSCs. This study suggests that, given the good capacity of retarding charge recombination, light harvesting capacity is the critical factor behind the photocurrent as well as the efficiency for organic dyes, but not the regeneration force of oxidized dyes.