Enhancing Performance and Stability of PEDOT:PSS-Based Organic–Inorganic Planar Heterojunction Solar Cells through Dimethyl Sulfone Doping

This paper presents a simple method of enhancing the performance and stability of a DMSO2 treated PEDOT:PSS film as a hole-transport layer in an organic–inorganic planar heterojunction solar cell. By integrating dimethyl sulfone (DMSO2 or D2 for short) alongside ethylene glycol and methanol, significant improvements in the power conversion efficiency (PCE), conductivity, morphology, and long-term stability are achieved. Notably, DMSO2 induces unique morphological reorganization leading to enhanced screening upon film drying, aligning PEDOT chains and thus enhancing electrical conductivity. Solar cells incorporating ethylene glycol and DMSO2 treated PEDOT:PSS films (ED2) are found to exhibit superior environmental stability, with an average T80 (the time taken for its PCE to decline to 80% of its initial as-fabricated value) of ∼913 h of ambient storage, with its as-fabricated PCE of 13.5 ± 0.7%. Devices employing ethylene glycol + methanol + DMSO2 treated PEDOT:PSS films (EMD2) show the highest as-fabricated PCE of 15.5% and an average T80 of ∼261 h of ambient storage, which can be attributed to the optimized morphology, improved film wettability, and favorable energy band alignment. Structural and chemical analyses using the van der Pauw conductivity measurements, atomic force microscopy, X-ray photoelectron spectroscopy, and time-of-flight secondary ion mass spectrometry confirm these findings, establishing DMSO2 as a promising green additive to enhance both performance and stability in planar heterojunction solar cells.