Molecular design of metal-free D-pi-A substituted sensitizers for dye-sensitized solar cells

Novel donor-pi-acceptor (D-pi-A) dyes, coded as SD-1, SD-2 and SD-5, were designed and synthesized for dye-sensitized solar cells. All these dyes comprised the same donor and acceptor units while the oligo thiophene units were introduced as linkers between the donor and acceptor units. The photophysical and electrochemical properties of the dyes were investigated by UV/vis spectrometry and cyclic voltammetry. The dyes were subsequently tested as sensitizers in dye-sensitized solar cells. Photovoltaic performance of the device with SD-2 dye showed maximum monochromatic incident photon-to-current efficiency (IPCE) of 82% and an over all conversion efficiency of 6.2% under full sunlight (AM 1.5G, 100 mW cm(-2)) irradiation.