The effect of bis-carboxylic groups of squarylium dyes on the efficiency of dye-sensitized solar cells

Symmetric squarylium dye (SQIND1) with bi-carboxylic groups has been synthesized and photoelectrochemical properties have been studied in comparison with its non-functionalized analog groups (SQIND2). The experimental results showed that the introduction of anchor carboxylic groups in SQIND1 sensitizer provides a more intimate contact with nanoparticles TiO2 which increases the number of charge carriers transferred from the SQIND1 to the semiconductor. The theoretical calculations and absorbance results show that the electron density of LUMO of SQIND1 is delocalized in the whole chromophore, leading to strong electronic coupling between SQIND1 sensitizer and conducting band of TiO2, resulting in improved dye-sensitized solar cell efficiency compared to SQIND2. Hence, the SQIND1 sensitized exhibit better photovoltaic performance. Although, the absence of any linker groups in the SQIND1, then SQIND1 was perfect efficiently sensitized on porous TiO2 with the long UV-Vis and NIR region up to 800 nm of the spectrum and showed higher remarkable performance of values, such as eta of 3.3%, a J(sc) of 7.6 mA/cm(2), a V-oc of 0.59, and FF of 0.73.