Spray-coated carbon nanotubes as alternatives to ITO electrodes for inverted perovskite solar cells

Abstract To fabricate a uniform spray-coated single-walled carbon nanotubes (wet-CNT) film as a replacement for an indium tin oxide substrate, a combination of ultrasonic treatment, centrifugation, and filtration was employed and systematically evaluated. Filtration effectively reduced carrier trap density, enabling to the fabrication of inverted perovskite solar cells with a glass/CNT/PEDOT:PSS/CH 3 NH 3 PbI 3 /C 60 /Ag structure. Furthermore, the wet-CNT film with vapor-transferred HNO 3 doping as a p-dopant, a significantly deeper energy level shift compared to the vapor deposition process based carbon nanotube (dry-CNT) film, likely due to water molecules on the CNT surface facilitating oxidation through interactions with HNO 3 . On the other hand, when AuCl 3 /IPA was employed as a dopant, the dry-CNT film, exhibited a greater energy level shift, attributed to the hydrophobic surface retaining Au 3+ ions more effectively.