Dielectric barrier discharge jet processed TiO2 nanoparticle layer for flexible perovskite solar cells

For attaining good-performance perovskite solar cells (PSCs), the carrier collection from the perovskite material to the transport layer plays a prominent role; herein, we demonstrate an atmospheric pressure plasma treatment technique to enhance the interface properties between the active perovskite layer and electron transport layer (ETL). A scan-mode low-temperature helium dielectric barrier discharge (DBD) jet is applied to process the TiO2 nanoparticle layers for the flexible n-i-p PSCs made on ITO-coated polyethylene naphthalate substrates. When the surface of TiO2 nanoparticle ETL is treated by the DBD jet at a scan rate of 2 cm s−1 and scan height of 5 cm by ten times, the photoelectrical conversion efficiency of the cell is enhanced from 12.30% to 13.66%. The performance improvement can be attributed to the increase of hydrophilic O–C = O functional groups on the surface of the TiO2 nanoparticle layer and the reduction of charge transfer resistance of the cell revealed by x-ray photoelectron spectroscopy and electrochemical impedance spectroscopy, respectively. The results show that the low-temperature DBD jet treatment is a promising technique for processing flexible photovoltaic devices.