Efficient dye sensitizers N,N'-dialkylcarbazolocarbazole derivatives BG-501 and BG-502 were synthesized and characterized. UV-vis, 1H NMR and CV were used for the structural characterization. The aim of the synthesis of these molecules is to improve some optical and electronic properties such as molar absorption coefficient, spectral coverage and electron injection properties of the sensitizers. Conjugated organic dyes exhibit higher molar extinction coefficients which allow harvesting more light in thinner semiconductor layer. Carbazole derivative dyes are well known in the literature with their thermal and photochemical stabilities and improved electron donor properties. We have achieved promising photovoltaic conversion efficiencies with new dyes BG-501 and BG-502 under standard conditions (AM1.5G, 100 mW. cm(-2) light intensity). The conversion efficiencies of solar cells are eta:3.18% and eta:2.49% with ionic liquid-based electrolyte for BG-501 and BG-502. respectively. (C) 2009 Elsevier B.V. All rights reserved.