<h3>Title</h3>
<h3><span style="font-size: 12.16px;">Ta doped compact TiO<sub>2</sub>  for improved performance in perovskite solar cells</span></h3>
<p><strong><span style="font-size: 12.16px;"><span style="text-decoration: underline;">Abstract</span> :</span></strong></p>
<p><span style="font-size: 12.16px;">Perovskite solar cells (PSCs) are currently the most exciting solar photovoltaic technologies for future deployment. A conventional PSC device structure typically employs a titanium dioxide (TiO<sub>2</sub>) electron transport layer. However, the low electrical conductivity of TiO<sub>2</sub> is an obstacle to PSC efficiency enhancement. In this work, we report on the conductivity enhancement of TiO<sub>2</sub> by tantalum (Ta) doping and its effect on improving the device performance. Photovoltaic measurements show that Ta doping of compact TiO<sub>2</sub> results in an improvement in the fill factor (FF) of the devices due to a decrease in the series resistance (Rs), attributed to improved charge transport and an increase in the shunt resistance (Rsh), due to reduced leakage paths.  Further it was found  that the Fermi level of TiO<sub>2</sub> shifts downward upon Ta doping providing driving force for the electron transfer from the perovskite LUMO to the TiO<sub>2</sub> conduction band resulting in higher current density. PSC devices with Ta doping of 3.0% led to a 40% improvement in the overall efficiency as compared to un-doped TiO<sub>2</sub> with the best device showing a power conversion efficiency of ca. 9.94%</span></p>