<p>This study investigated diketopyrrolopyrrole-spacer-based dye sensitizers for dye-sensitized solar cells (DSSCs) applications, specifically the effects of electron-donating and electron-withdrawing groups on donor moieties. Using the computational methods, we evaluated the photophysical properties and efficiency metrics like light harvesting efficiency, electron injection efficiency, regeneration efficiency, and overall solar energy conversion efficiency, and compared them with the existing experimental results. Further, we have predicted better and more efficient dyes with small changes, like adding electron-donating groups on the para position of the donor moieties with density functional theory. The three donor groups: carbazole (CB), diphenylamine (DA), and indole (IN)- and their derivatives with electron-donating and electron-withdrawing substituents were examined.</p> Graphical abstract <p>Electron-donating groups on donor groups enhances the efficiency whereas electron-withdrawing groups reduces the efficiency.</p>