Beyond Conventional Enhancements: Self‐Organization of a Buffer Material on Tin Oxide as a Game‐Changer for Improving the Performance of Inverted Organic Solar Cells

Inverted organic solar cells (OSCs) have garnered significant interest due to their remarkable stability. In this study, the efficiency and stability of inverted OSCs are enhanced via the in situ self‐organization (SO) of an interfacial modification material Phen‐NaDPO onto tin oxide (SnO2). During the device fabrication, Phen‐NaDPO is spin‐coated with the active materials all together on SnO2. Driven by the interactions with SnO2 and the thermodynamic forces due to its high surface energy and the convection flow, Phen‐NaDPO spontaneously migrates to the SnO2 interface, resulting in the formation of an in situ modification layer on SnO2. This self‐organization of Phen‐NaDPO not only effectively reduces the work function of SnO2, but also enhances the ordered molecular stacking and manipulates the vertical morphology of the active layer, which suppress the surface trap‐assisted recombination and minimize the charge extraction. As a result, the SO devices based on PM6:Y6 exhibit significantly improved photovoltaic performance with an enhanced power conversion efficiency of 17.62%. Moreover, the stability of the SO device is also improved. Furthermore, the SO ternary devices based on PM6:D18:L8‐BO achieved an impressive PCE of 18.87%, standing as one of the highest values for single‐junction inverted organic solar cells to date. In this study, an in situ self‐organization strategy is utilized to passivates electron transport layer defects, promotes vertical component distribution of active layer, and enhance efficiency and stability in inverted organic solar cells, achieving an impressive PCE of 18.87% in ternary cells.