Effect of thiophene rings rigidity on dye-sensitized solar cell performance. Dithienothiophene versus terthiophene as [Formula: see text] donor moiety

Solar cells are fabricated based on two new dyes. Dye acts as an additive to thin layer interface. The effect of the [Formula: see text]-conjugated rigidity of the thiophene rings on the photovoltaic characteristics has been investigated. The structures of the dye 1 was based on dithieno [3,2-b:2′,3′-d] thiophene-2-cyanoacrylic acid, while dye 2 was based on [2,2':5′,2″-terthiophene]-5-cyanoacrylic acid and were confirmed by elemental analysis, mass spectrometry, (1)H NMR and (13)C NMR spectral data. The P3HT/dye 1/nc-TiO(2) solar cell produced the highest efficiency of 0.3 % with an open circuit voltage of 0.7 V compared to dye 2 solar cell. This has been attributed to the difference in energy levels of the dyes and location of their HOMO relative to conduction and valence bands of nc-TiO(2). The dye 1 has rigid fused thiophene rings and its HOMO is located between valence band of TiO(2) and HOMO of P3HT which leads to improve the charge carrier separation and increase the current density to reach 1.2 mA/cm(2).