**Abstract**

Ligand with conjugated π systems presents high planar and delocalized electronic density, which allows it to capture the radiations with an energy interval of wavelengths between 400 and 600 nm. The ligands can be linked to inorganic materials favoring the interchange in the system. Lewis acids improve the electronic distribution between donor and acceptor favoring the optical and electronic properties, yielding superior efficiencies. In this chapter, the evolution of the ligands such as Porphyrins, Metal-free organic dyes, and Ruthenium complexes used, and the construction of solar cells is described. In this context, three different small-molecule acceptors-donors are reported; *o*-PDT, *m*-PDT and *p*-PDT, based on phenyldiammine (PD) as spacer, and Thiazole (T) were designed and synthesized. There were estimated electronic, optical and photovoltaic parameters for these molecules. The interaction energies of functional groups for PD and T molecules, with DFT/B3LYP method, gas phase with 6-31g (d, 2p) basis sets, were represented and computed. The best photovoltaic parameters were described for *p*-PDT with PCE 26.18%, Jsc = 14.79 mAcm<sup>2</sup> and ΔE = 2.66 eV. The metal ion influences the electronic properties and decreases the ΔE GAP. The incorporation of the transition metals into hyperconjugated systems provides rigidity and effects of electronic back donation.

**Keywords:** photovoltaic cells, semiconductor, coordination compounds, dye-sensitized
