Regular Article

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

¹ Department of Electrical and Computer Engineering, University of Canterbury, Christchurch, 8041, New University of Canterbury, Christchurch, New Zealand
² The MacDiarmid Institute for Advanced Materials and Nanotechnology, Wellington 6140, New Zealand

^* e-mail: ahmed.hayali@pg.canterbury.ac.nz

Received: 2 March 2021
Received in final form: 20 October 2021
Accepted: 26 October 2021
Published online: 19 November 2021

Abstract

High conductivity and transparency of the electron-transporting layer (ETL) is essential to achieve high efficiency perovskite solar cells (PvSCs). Generally, titanium dioxide (TiO₂) has been extensively utilized as an ETL in PvSCs. Both surface roughness and uniformity of the compact-TiO₂ (C-TiO₂) 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 (O₂) plasma to achieve high quality ETL films. The effect of changing the DC sputtering power on the C-TiO₂ films and subsequently on the overall efficiency was studied. The electrical and optical properties of the C-TiO₂ layer were characterized for various DC powers and different ratios of Ar to O₂ plasma. It was found that the optimum preparation conditions for the C-TiO₂ films were obtained when the DC power was set at 200 W and a flow rate of 6 sccm Ar and 12 sccm O₂. 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/cm². These results indicate that significant improvement in the efficiency can be achieved, by optimizing the C-TiO₂ layer.