Light controlled assembling of iodine-free dye-sensitized solar cells with poly(3,4-ethylenedioxythiophene) as a hole conductor reaching 7.1% efficiency

We report the fabrication of indoline D205 dye-sensitized solar cells (DSSCs) with photoelectrochemically polymerized poly(3,4-ethylenedioxythiophene) (PEDOT) as a hole conductor. Different from conventional photoelectrochemical polymerization under continuous spectral light illumination (e.g. Xe lamp), we conduct the polymerization under monochromatic light. The device performance is found to be dependent on the wavelength of monochromatic light used for the polymerization of PEDOT. Under optimized conditions, the efficiency of DSSCs reaches 7.1%, which is better than that of devices fabricated via continuous spectral light illumination. Detailed characterization of these devices with photoelectrical and impedance measurements reveals that the wavelength of monochromatic light affects PEDOT penetration into TiO2 porous electrodes and photoelectron recombination at the FTO surface. The best device performance is obtained when penetration and recombination are optimized.