Ambient processed perovskite sensitized porous TiO₂ nanorods for highly efficient and stable perovskite solar cells

One dimensional (1-D) TiO₂ nanorod (NR) scaffold layers are considered to be a superior electron transporting layer (ETL) for perovskite solar cells (PSC) as compared to TiO₂ nanoparticles (NP) in relation of morphological and electronic properties. Rutile phase porous TiO₂-NR has been grown with different lengths and porosity via the hydrothermal method. Porosity and length of the rods are controlled by varying the reaction time and concentration of the precursor solution. Change in the morphology and their effect on the photovoltaic and charge transport properties are investigated deeply through scanning electron microscopy, current density voltage (J-V) curves and electrochemical impedance spectroscopy (EIS). The synthesized TiO₂-NR and NP-TiO₂ electrodes are used to fabricate ambient processed PSCs. Compared to the conventional NP-TiO₂ based PSC device, the device is prepared with the 350 nm porous TiO₂-NR has shown improved power conversion efficiency (14.0%). Such enhancement in photovoltaic performance arises from uniform infiltration of perovskite into the scaffold layer, which enhances the light collection efficiency and increases electron-transport property. Furthermore, the NR based PSC devices have retained 80% of its initial performance even after 50 days of being stored in ambient conditions (relative humidity (RH) - 60%). These results further emphasize the use of 1-D NR as ETL for ambient processed PSC with improved stability.