Oxoammonium enabled secondary doping of hole transporting material PEDOT:PSS for high-performance organic solar cells

Poly(3,4-ethylenedioxythiophene):polystyrene sulfonate(PEDOT:PSS)is one of the most widely used hole transporting materials in organic solar cells(OSCs).Multiple strategies have been adopted to improve the conductivity of PEDOT:PSS,however,effective strategy that can optimize the conductivity,work function,and surface energy simultaneously to reach a better energy alignment and interface contact is rare.Here,we demonstrate that oxoammonium salts(TEMPO^+X^-)with different counterions can act as facile and novel dopants to realize secondary doping of PEDOT:PSS.The effective charge transfer process achieved between TEMPO^+X^-and PEDOT:PSS results in enhanced carrier density and improved conductivity of PEDOT:PSS.Moreover,different counterions of TEMPO^+X^-can tune the work function and surface energy of PEDOT:PSS,enabling improved device performances.The resulting device with PM6:Y6 as the active layer shows a high power conversion efficiency(PCE)over 16%.Moreover,this doping strategy can also be applied to other conjugated polymers such as poly(3-hexylthiophene).This work provides a promising strategy to tune the properties of conjugated polymers through doping,thus effectively boosting the performance of organic solar cells.