Photoanodes based on titanium dioxide (TiO2) are ubiquitous in various molecular devices for solar energy conversion and storage.[1] Lanthanide doping of TiO2 (LTO) is among the most explored materials with tremendous potential towards efficient charge transport mesoporous layer as well as improving the photocatalytic activity in both solar cell and solar fuel devices.[2, 3] In this work, presented a comprehensive investigation of improved performance of Samarium (Sm3+)-doped TiO2 based dye-sensitized solar cells (DSSC) and Photo-electrochemical (PEC) devices and established the optimum Sm3+ doping of TiO2 by characterizing the different Sm3+concentrations (0.1-0.5 mol%). Various techniques, namely, X-ray diffraction (XRD), scanning electron microscope (SEM), UV-VIS absorption spectroscopy, are employed for an all-inclusive characterization of the prepared Sm-TiO2 samples. The dielectric measurements on Sm-TiO2 pellets established the best electrical conductivity exhibited by Sm (0.4%)-TiO2. Synthesis protocols are followed based on earlier work.[3] The photoanodes based on prepared Sm-TiO2 are deposited on FTO substrates and are used to fabricate DSSC and PEC devices. Commercial N719 dye-based DSSC devices are fabricated and tested. Devices with Sm(0.3%)-TiO2 exhibited power conversion efficiency (ζ) 6.4%, which is almost 100% improvement on devices with undoped-TiO2 that exhibited ζ: 3.4% as shown in Figure 1. Time-resolved PL-quenching measurements evidenced better electron-injection at dye/Sm (0.3%)-TiO2 interface. Similarly, PEC devices presented higher current density at 1.2 V vs RHE potential for Sm (0.3%)- TiO2. This enhancement corroborates the EIS measurements presenting lower charge transfer resistance values for devices with Sm (0.3%)-TiO2. © 2021 SPIE.