Acid Doping of PEDOT:PSS\nStrengthens Interfacial Compatibility\ntoward Efficient and Stable Perovskite Solar Cells

Poly(3,4-ethylenedioxythiophene):poly(4-styrenesulfonate)\n(PEDOT:PSS)\nhas been widely applied as a hole transport material in s. Although PEDOT:PSS\nexhibits the advantages of superior conductivity and low material\ncost, the corresponding devices suffer from low photovoltaic performance\ndue to unsatisfactory interfacial properties. Here, an acid treatment\nstrategy is developed to modify the chemical properties of PEDOT:PSS\nby different HX (X = Cl, Br, I) acids. We present evidence of an effective\nion exchange process between HX and PEDOT:PSS and show that the anion-dependent\ndedoping of PEDOT:PSS leads to large variation of thin-film conductivity,\nfilm hydrophilicity, and interfacial contact between perovskite and\nPEDOT:PSS. PEDOT:PSS treated by HCl demonstrates optimal interfacial\ncompatibility along with superior charge collection efficiency, which\ncontributes to significantly enhanced device efficiency (17.63%) compared\nto the control device (14.56%). Moreover, the resulting unencapsulated\ndevices based on HCl show superior long-term stability, maintaining\nmore than 90% of their initial efficiency after 2355 h, whereas the\ncontrol device only kept about 47% of original PCEs after 1120 h.\nThis work indicates the effectiveness of acid treatment in modulating\nthe doping properties of PEDOT:PSS and provides an efficient way to\nimprove the interfacial performance of perovskite solar cells.