High efficiency perovskite solar cells using DC sputtered compact TiO₂ electron transport layer

Abstract

High conductivity and transparency of the electron-transporting layer (ETL) is essential to achieve high efficiency perovskite solar cells (PvSCs). Generally, titanium dioxide (TiO 2 ) has been extensively utilized as an ETL in PvSCs. Both surface roughness and uniformity of the compact-TiO 2 (C-TiO 2 ) can influence the efficiency of the PvSC. This work investigates the optimization of the direct current (DC) sputtering power and the ratio of argon (Ar) to oxygen (O 2 ) plasma to achieve high quality ETL films. The effect of changing the DC sputtering power on the C-TiO 2 films and subsequently on the overall efficiency was studied. The electrical and optical properties of the C-TiO 2 layer were characterized for various DC powers and different ratios of Ar to O 2 plasma. It was found that the optimum preparation conditions for the C-TiO 2 films were obtained when the DC power was set at 200 W and a flow rate of 6 sccm Ar and 12 sccm O 2 . A power conversion efficiency (PCE) of 15.3% in forward sweep and 16.7% in reverse sweep were achieved under sunlight simulator of 100 mW/cm 2 . These results indicate that significant improvement in the efficiency can be achieved, by optimizing the C-TiO 2 layer.