Herein we present a comprehensive study of composition dependent Neodymium (Nd3+) doped Titania (Nd-TiO2) as photoanodes for obtaining improved performances in different types of solar energy conversion devices, namely dye-sensitized solar cell (DSSC), quantum-dot (QD) sensitized solar cells (QDSC) and photo-electrochemical cells (PEC). An all-inclusive characterization of the optical, dielectric properties and morphological studies of Nd-TiO2 with different doping concentration are performed. The XPS and Urbach energy analysis corroborated further by the dielectric studies established the critical role of vacancies in the improved electrical properties of doped TiO2 in comparison with that of undoped TiO2. Superior performances on solar cells devices (DSSC and QDSC) and PEC water splitting devices using N719 dye and CdS-QD sensitized Nd-TiO2 photoanodes were fabricated and analyzed. Enhanced photo-conversion efficiencies of ≈30% for QDSC and ≈16% for DSSC were obtained with Nd (0.4 mol%)-TiO2 photoanodes in comparison with undoped TiO2 photoanodes. Similarly, the PEC water splitting of CdS (QDs) sensitization exhibited the photocurrent density of (1.8 mA-cm−2 at 1.23 V vs RHE), which is three times higher than undoped TiO2, while the N719 dye-sensitized photoanode exhibited the current density of (0.7 mA-cm−2 at 1.23 V vs RHE), which is two times higher than undoped TiO2. The results established that the optimized doping concentration of Nd (0.4 mol%)-TiO2 is universal for all classes of solar energy conversion devices. © 2020 Elsevier B.V.