Cooperative Effect of Carbon Nanotubes and Dimethyl Sulfoxide on PEDOT: PSS Hole Transport Layer in Planar Perovskite Solar cells

:poly(styrene sulfonate) (PEDOT:PSS) film is commonly used as hole transport layer in planar perovskite solar cells (PSCs). To further strengthen the charge transport within PEDOT:PSS film and boost the growth of the perovskite crystal on PEDOT:PSS film, carbon nanotubes (CNTs) and dimethyl sulfoxide (DMSO) were simultaneously used as additives to prepare the co-modified film of CNT-DMSO-PEDOT:PSS. Results demonstrate an advantageous cooperative effect of CNTs and DMSO on the co-modified film. The dispersed CNTs with a grid-like structure throughout PEDOT:PSS matrix plays dual roles: to promote the perovskite crystal growth on co-modified surface and to reduce the sheet resistance of the co-modified film, while DMSO improves the conductivity of the co-modified film and controls the loss of CNTs from the co-modified film. Due to the cooperative effect, co-modified film is significantly more capable to collect, transport charges and enhance the perovskite layer growth with larger grains on its surface than that with pristine PEDOT:PSS film or PEDOT:PSS films modified by a single additive of CNT or DMSO, CNT-PEDOT:PSS or