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‐Shafei, Airody Vasudeva Adhikari
Abstract
Abstract 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 . S 1‐3 having different structural designs, that is, D‐π‐A ( S 1 ), D‐D‐π‐A ( S 2 ), and A‐π‐D‐π‐A ( S 3 ) 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 S 3 exhibited improved PCE of 3.77 % due to its strong adsorption on the TiO 2 surface that resulted in superior V OC of the cell. While the S 2 containing electron‐releasing anisole as an auxiliary donor exhibited better J SC value leading to the optimum PCE of 3.73 % which is comparable to that of S 3 . Obviously, these results validate the role of the π‐spacer and additional donor of the sensitizers on the overall performance of the DSSCs.