Contribution in Light Harvesting by Solid Ionic Conductors for Efficient Photoelectrochemical Cells: An Effect of an Identical Donor Molecule in Sensitizers and Electrolytes

We report here the rational architecture of heteroanthracene-based metal-free organic D−π–A sensitizers (DS-1 and DS-2) and solid organic redox shuttles (ORSs) with common donor moieties phenothiazine (PTZ) and phenoxazine (POZ) developed for solid-state dye-sensitized photoelectrochemical cells (DS-PECs). The introduction of identical donor moieties in sensitizers and electrolytes has a positive bearing on the visible light absorbance, favorable electron lifetimes, and facile electron injection into the nanocrystalline TiO2 photoanode. The synthesized metal-free sensitizers with compatible solid-state ORSs are characterized using optical, electrochemical, and theoretical parameters. The solid-state DS-PEC sensitized using POZ-substituted DS-2 and ORS electrolyte shows a maximum power conversion efficiency (PCE) of ∼8.7% upon 100 mW cm–2 illumination owing to the photochemical interaction between the sensitizer and the electrolyte. Influence of electron and energy distribution over the sensitizer molecules in the presence of a similar donor moiety-substituted ORS is calculated using density functional theory and compared with experimental results. In addition, both sensitizers with a single-component ORS (dopant-free) displayed an excellent PCE of ∼6.3%. It was also observed that the DS-2 photochemical device exhibited long term stability for more than 1600 h.