Fig. 4: Schematics illustrating the formation of double-layer PEDOT:PSS and the resultant device performance.

a Illustration on the fabrication of reference PEDOT:PSS film and (b) corresponding statistical distribution of power conversion efficiency (PCE) for NBG PSCs, 50 cells included. c Illustration on the fabrication of PEDOT:PSS film with Triton X-100 and (d) corresponding statistical distribution of PCE, 65 cells included. e Illustration on the post-deposition treatment (PDT) for the reference PEDOT:PSS films with water or Triton X-100. f Statistical distribution of PCE for NBG PSCs with water wash (23 cells included) or (g) with Triton X-100 wash on PEDOT:PSS (52 cells included). h Illustration on possible electric dipoles forming at the top surface of the reference PEDOT:PSS film, and (i) reduced electric dipoles with Triton X-100. In (b, d, f, g), horizontal bars indicate the 25–75 percentile, mean, and minimum/maximum values, respectively. The distribution is fitted with the Gaussian function (solid line).