Silicon telluride (Si2Te3) is a two-dimensional, layered, p-type semiconductor that shows broad near-infrared photoluminescence. We show how, through various means of chemical modification, Si2Te3 can have its optoelectronic properties modified in several independent ways without fundamentally altering the host crystalline lattice. Substitutional doping with Ge strongly red-shifts the photoluminescence while substantially lowering the direct and indirect band gaps and altering the optical phonon modes. Intercalation with Ge introduces a sharp 4.3 eV ultraviolet resonance and shifts the bulk plasmon even while leaving the infrared response and band gaps virtually unchanged. Intercalation with copper strengthens the photoluminescence without altering its spectral shape. Thus, silicon telluride is shown to be a chemically tunable platform of full spectrum optical properties promising for optoelectronic applications.