Pathway to the Polyvinyl-Acetate-Assisted PEDOT:PSS as a Dopant-Free Hole Transporting Material in Planar Heterojunction Perovskite Solar Cells

To achieve world's burgeoning appetite in obtaining high-energy conversion efficiency, not only perovskite semiconductor but also hole transporting material (HTM) takes a significant role as a game changer. The dopant of conventional organic HTM induces side effects of degradation, and inorganic HTM reacts or penetrates with the underlying perovskite layer. Considering those issues, poly(3,4-ethylenedioxythiophene:poly(styrene sulfonate) (PEDOT:PSS) as an alternative HTM has been explored in the field of perovskite solar cells with its outstanding hole transporting property. Herein, incorporation of polyvinyl acetate (PVAc) in PEDOT:PSS paves the way to wide applications in device structural perspective, as to say, in n-i-p structure. The presence of the ester group in PVAc donates the bonding site to the perovskite layer, which improves the adhesion, resulting in enhanced charge transport ability as well as device stability. PVAc-treated PEDOT:PSS device exhibited 20% higher power conversion efficiency (PCE) than the PVAc-free device and retained 80% of initial PCE after 1000 h under extreme conditions (AM 1.5G and 60 degrees C).