Enhanced planar perovskite solar cells with efficiency exceeding 16% via reducing the oxygen vacancy defect state in...

In this work, the influence of oxygen vacancy defect (OVD) in compact titanium oxide (c-TiO₂) on the performance of planar perovskite solar cells (p-PSCs) is investigated, and the possible mechanisms are also proposed. To meet our objective, anatase c-TiO₂ thin films with various OVD concentrations are prepared by changing the oxygen flux during the DC magnetron sputtering process and are characterized by the intensity of defect signals in the X-ray photoelectron spectra. We conclude that abundant OVDs can trigger an obviously increased majority carrier accumulation zone at the metal oxide/perovskite interface and enhanced capacitance, thereby greatly deteriorating photogenerated carrier collection efficiency. A detailed analysis of the study results also reveals that the presence of OVD in the bulk and surface of c-TiO₂ can slow down electronic carrier transport and lower its electron quasi-Fermi level under illumination, leading to the detrimental charge recombination in p-PSCs. Furthermore, we report a remarkably enhanced p-PSC efficiency via preparing c-TiO₂ using high oxygen flux and subsequent ultraviolet ozone treatment. As a consequence, repeatable power conversion efficiency (PCE) is propelled to as high as 16.62%, coupled with negligible hysteresis and increased stability. These results provide a significant implication for further perfecting efficient and stable p-PSCs for their record efficiency.