A Facile Aqueous-Processed MoO ₃ Buffer Layer for Efficient and Stable Organic Solar Cells

Interface engineering is widely recognized as a key strategy for boosting both the performance and longevity of devices, thereby significantly contributing to the feasibility and success of organic solar cells (OSCs) in the market. In this work, we present a facile aqueous-based fabrication scheme for the introduction of an ultrathin MoO3 buffer layer, which exhibits excellent ion-blocking capability between indium–tin oxide and poly(3,4-ethylenedioxythiohene):poly(styrenesulfonate) (PEDOT:PSS) in conventional OSCs. The MoO3 buffer layer is deposited onto the substrate via spin-coating, utilizing a colloidal dispersion of MoO3 nanoparticles (NPs) synthesized through a low-temperature hydrothermal method. The MoO3 buffer layer not only effectively inhibits the corrosive effects associated with PEDOT:PSS but also improves energy-level matching at the hole-transport layer (HTL)/active layer interface, thereby enhancing the process of hole extraction. Accordingly, OSCs incorporating the MoO3/PEDOT:PSS structure attain a power conversion efficiency (PCE) of 18.67%, exhibiting a notable improvement over the control OSCs (PCE = 17.58%) based on the PEDOT:PSS HTL. Remarkably, unencapsulated devices maintain 82% of the initial efficiency following 750 h of storage in a glovebox, representing good stability for potential practical applications.