Influence of π-linkers and electron accepting substitutions on phenothiazine-based D-A-π-A dyes for DSSC applications: A DFT and TDDFT study

This research introduces the design of a novel series of D-A-π-A organic dyes, achieved by modifying the external acceptor and various π_i-spacers based on the synthesized dye PTZ15R, aiming to improve the photovoltaic performance of dye-sensitized solar cells (DSSCs). The influence of changing the external acceptor and various π-spacers on the properties of these sensitizers was theoretically investigated using density functional theory (DFT) and time-dependent density functional theory (TD-DFT) methods to reveal structure-property relationships. Calculations show that replacing the carboxylic group with cyanoacrylic acid and benzene (π_original) with electron-deficient groups (PTZ15AD1 to PTZ15AD9) significantly reduces the energy gap and broadens the absorption spectrum for all investigated dyes, which will result in higher V_OC and J_SC than the reference PTZ15R. These findings suggest that the newly designed dyes are promising sensitizers for DSSCs, with dye PTZ15AD6 being particularly noteworthy due to its planar structure, small energy gap, longer absorption wavelength, excellent chemical reactivity parameters, higher NLO properties, and more significant dipole moment both in isolated and adsorbed states. This theoretical investigation aims to provide new strategies for synthesizing and predicting efficient sensitizers for DSSCs.