Tuning the photovoltaic performance of biogenic hydroxyapatite via Ti-doping: Mechanistic insights from DFT and experimental characterization

The efficiency of biogenic-sourced photoanodes for dye-sensitized solar cells (DSSCs) is governed by their optical bandgap and electronic structure. This study investigates titanium (Ti) doping of clam shell-derived hydroxyapatite (HAp) through combined experimental and computational approaches. Ti4+ substitution into the hexagonal HAp lattice introduces Ti-3d donor states near the conduction band, narrowing the bandgap from 6.78 eV (pristine) to 2.30-3.08 eV (Ti-doped). DFT simulations confirm that Ti4+ substitution at Ca(I) sites induces localized polyhedral distortions while preserving the apatite framework. The optimized Ti-HAp photoanodes achieved a mean power conversion efficiency (PCE) of 0.354% ± 0.022, representing a 153% improvement over previously reported biogenic HAp-based DSSCs (0.14%). This work demonstrates Ti-doping as an effective strategy for tuning the electronic properties of eco-friendly ceramics for sustainable energy applications.