Hydrothermal synthesis of TiO2 nanoparticles doped with trace amounts of strontium, and their application as working electrodes for dye sensitized solar cells: tunable electrical properties & enhanced photo-conversion performance

Abstract

Strontium (Sr) doped TiO₂ nanoparticles are investigated with a view to studying the performance parameters of dye sensitized solar cells (DSSCs). Sr is used in trace levels (parts per million, ppm hereafter). The Sr doped TiO₂ and undoped TiO₂ nanoparticles are synthesized by the hydrothermal method and thin films of TiO₂ electrodes are prepared using these particles (average grain size of 24 nm). The electrodes are characterized by X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), surface area (BET) and UV-vis absorption spectrometry. DSSCs are fabricated using the doped and undoped TiO₂ nanoparticle photoanodes. Their photovoltaic characteristics are studied by employing J–V measurements and electrochemical impedance spectroscopy (EIS). XRD studies reveal that the doping of Sr into the TiO₂ lattice slightly inhibits the growth of the particles and causes lattice distortions. The optical studies indicate a reduction in band-gap upon doping of TiO₂ films and a simultaneous enhancement in the photocurrent density (J_sc) and the photovoltage (V_oc). The photoanode doped with 50 ppm Sr exhibits the highest power conversion efficiency (PCE) of about 7.88% which is 12.73% higher than that of undoped TiO₂ cells. The effect of the Sr dopant on electron transport is studied by using EIS measurements. An improvement in electron life time is observed on the doping of TiO₂.