Modified HTL-induced efficiency enhancement for inverted perovskite solar cells

Abstract Poly(3,4-ethylene dioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) was doped by 3-(Cyclohexylamino)-2-hydroxy-1-propanesulfonic acid (CAPSO), leading to dramatic improvement of its conductivity and consequently efficiency enhancement in inverted perovskite solar cells (PSCs) based on PEDOT:PSS hole transport layer (HTL). Under the optimized CAPSO doping concentration, the conductivity of PEDOT:PSS film increased by about three orders of magnitude, and this is interpreted by the weakening of the coulombic attractions between PEDOT and PSS components induced by CAPSO. CAPSO doped PEDOT:PSS (PEDOT:PSS@CAPSO) was applied as HTL of PSCs devices based on CH3NH3PbI3 layers, leading to the best power conversion efficiency (PCE) of ~38% enhanced relative to those of the corresponding reference devices based on pristine PEDOT:PSS HTL. Scanning Kelvin probe microscopy (SKPM) results show that the work function of PEDOT@CAPSO matches well with the valence band of CH3NH3PbI3 absorbers. The research demonstrates that the zwitterion modified PEDOT:PSS could act as an outstanding hole transport material for fabricating high-efficient perovskite solar cells.