In this review, the introduction of solar cells is presented. Old and new generation solar cells are briefly described. Quantum dot solar cells (QDSCs), perovskite solar cells, and dye-sensitized solar cells (DSSCs) are concisely introduced. The sensitization mechanism in DSSCs is discussed in detail concerning the spectral and electron injection properties of different dyes. An analysis of the intramolecular charge transfer process in the excited dye molecule is also provided. The use of porphyrin-based dyes as sensitizers in DSSCs is then reviewed. The design, synthesis, and photovoltaic application of a wide variety of porphyrin-based dyes as well as porphyrin dyads are presented and discussed. Theoretical studies of the spectral and electronic properties of different porphyrin-based dyes using DFT and TD-DFT methods are described. The different possibilities for improving the light-to-electrical energy conversion performance are discussed, such as structural modifications through introducing push-pull moieties, which in turn tunes the HOMO-LUMO energy gap of the sensitizing dye used in the DSSC. Experimental, as well as theoretical calculations of adsorption energies of the sensitizing dyes, are crucial for predicting the relative performance and efficiency of the dyes.