New naphthalenediimides as potential dyes for TiO 2 -sensitized solar cells

In this work new naphthalenediimides (NDIs) were synthesized and used as dyes in DSSC. The efficiency (η) of the DSSC is influenced by NDIs electronic and structural characteristics. It was found a better cell performance with the NDIs which have a broader absorption band shifted to the red color, high ƹ values, and more adsorption in the anode surface. The band gaps were determinate by UV–vis and cyclic voltammetry. The LUMO orbitals of most of the NDIs are above of the conduction band (CB) energy for TiO2 allowing the electron transfer process from the NDI to the photoanode, especially in those with a significant LUMONDI-CBTi energetic difference. Also, NDIs with polar groups in their structure presented higher η values due to a better adsorption on the photoanode surface, which allows a better energy capture compared with those with lower adsorption.