Carbazole based organic dyes as effective photosensitizers: A comprehensive analysis of their structure-property relationships
Praveen Naik, Kavya S. Keremane, Mohamed R. Elmorsy, Ahmed El-hafei, Airody Vasudeva Adhikari
Electrochemical Science Advances
The present work describes the effect of structural modification of carbazole-based photosensitizers carrying carboxylic acid as a common anchoring functionality, on the photovoltaic parameters of newly fabricated DSSCs. In this study, we have selected our previously reported three carbazole-based derivatives, viz. S1-3 having different structural designs, that is, D-π-A (S1), D-D-π-A (S2), and A-π-D-π-A (S3) with different donor units and π-spacers, but an identical cyanoacetic acid anchoring unit. We have evaluated their optical, electrochemical, and photovoltaic behaviors in order to explore their structure-property relationships. Also, the theoretical investigations were performed to obtain a deeper understanding of their HOMO-LUMO levels, charge distribution in FMOs, directional flow of electrons within the push-pull type sensitizers, and optical behavior. Finally, the DSSCs were constructed by employing these dyes as sensitizers without any co-absorbents and the performance of the devices was evaluated by using illuminated current-voltage characteristics. Among the tested dyes, di-anchoring S3 exhibited improved PCE of 3.77 % due to its strong adsorption on the TiO2 surface that resulted in superior VOC of the cell. While the S2 containing electron-releasing anisole as an auxiliary donor exhibited better JSC value leading to the optimum PCE of 3.73 % which is comparable to that of S3. Obviously, these results validate the role of the π-spacer and additional donor of the sensitizers on the overall performance of the DSSCs.
structural modification, photosensitizers, DSSCs,