We report key results of a systematic computational investigation using density functional theory along with the two standard Perdew–Burke–Ernzerhof and hybrid Heyd–Scuseria–Ernzerhof (HSE06) exchange–correlation formalisms on essential fundamental parameters for solar energy conversion of a series of large, medium, and small selected (covalent, binary, and ternary) materials widely utilized in fuel cells, photocatalysis, optoelectronics, photovoltaics, and dye-sensitized solar devices such as BN, AlN, C, ZrO2, Na2Ta4O11, Bi4Ti3O12, ZnS, GaN, SrTiO3, TiO2, Bi12TiO20, SiC, WO3, TaON, ZnSe, BiVO4, CuNbO3, CdS, AlP, ZnTe, GaP, Cu2O, AlAs, Ta3N5, BP, CdSe, SnWO4, GaAs, CdTe, and Si. Our calculations highlight that the optoelectronic and redox parameters computed with HSE06 reproduce with very good accuracy the experimental results, thanks to precise electronic structure calculations. Applying this first-principle quantum methodology led us to provide a rational design of new suitable solid solution materials for visible light-driven photochemical water splitting. This valuable computational tool will be applied to predict promising candidates to be experimentally prepared and tested for solar-to-chemical energy conversion.