UV–Ozone-Modified PSS-Free PEDOT Enhances Interfacial Contact in Regular Perovskite Indoor Photovoltaics

Indoor photovoltaics (IPVs) operate under low-intensity artificial lighting, where device performance is governed primarily by interfacial voltage-related losses rather than bulk charge transport. In this study, we investigate interfacial engineering of a dopant-free, PSS-free conducting polymer hole-transport material (HTM) based on poly(3,4-ethylenedioxythiophene) (PEDOT) for perovskite IPVs. Equimolar mixed-halide FA 0.85 Cs 0.15 PbI 1.5 Br 1.5 absorbers with a wide bandgap of 1.86 eV were implemented in regular device architectures tailored for indoor operation. UV–ozone treatment was employed to modify the surface chemistry and electronic structure of PEDOT. Under 1000 lx illumination, treated devices exhibited enhanced open-circuit voltage, fill factor, and shunt resistance, despite reduced short-circuit current density. X-ray and ultraviolet photoelectron spectroscopy reveal increased work function and oxygen-containing surface groups without disruption of the PEDOT backbone, leading to improved interfacial energetics and suppressed shunt-related losses. These results demonstrate that controlled surface chemical tuning of dopant-free polymeric HTMs enables efficient and reliable perovskite IPVs.