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

Poly(3,4-ethylenedioxythiophene):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 grams 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 DMSO-PEDOT:PSS. Meanwhile, the co-modified film maintains high transparency with a transmittance of 88.8% at 550 nm. As a result, the PSCs of co-modified film has a hig power conversion efficiency of 5.75% in contrast to the devices based on the CNT-PEDOT:PSS (3.01%), DMSO-PEDOT:PSS (2.03%) and pristine PEDOT:PSS (1.30%) films.