Theoretical Study of Effects of Anchoring Groups on Photovoltaic Properties of a Triarylamine-Based p-Type Sensitizer

Abstract

The effects of anchoring groups on triarylamine-based p-type dyes were studied by substituting the strong electron-withdrawing carboxyl group with the weak electron-withdrawing pyridyl and the electron-rich catechol groups. Judged by the index <i>t</i>, the charge separation would be improved greatly when the carboxyl group of <b>P4</b> is replaced by the pyridyl or catechol groups. Although carboxyl as an anchoring group lowers the HOMO energy and facilitates the hole injection in comparison with pyridyl and catechol groups, the weak electron-withdrawing pyridyl and the electron-rich catechol groups facilitate the charge separation. <i>E</i> _g becomes narrow as the electron-withdrawing abilities of the anchoring groups decrease or as the conjugation extends. Both the extended π-spacers and the substitution of carboxyl with pyridyl and catechol groups promote the redshifts of adsorption wavelengths. The oscillator strengths for all dyes are over 2.00, indicating that all the dyes are able to harvest the sunlight strongly. The Δ<i>G</i> _CR values of <b>P4</b>, <b>DF4</b>, and <b>DZ4</b> are smaller than those of the other dyes. Also, these dyes have larger adsorption over infrared visible light, indicating that these dyes may be good candidates for p-type DSSCs.