High-efficiency ternary layer-by-layer all-polymer solar cells enabled by a dual-donor alloy strategy

All-polymer solar cells (all-PSCs) exhibit the advantage of superior stability due to the intrinsic properties of the polymer with larger molecular sizes. However, obtaining excellent morphology of the active layer is an important challenge for achieving efficient all-PSCs. In this work, a ternary-assisted layer-by-layer (LbL) strategy is used to optimize the morphology of all-PSCs. The polymers PM6, PM1, and PY-IT are selected as host donor, guest donor, and acceptor to fabricate a series of LbL all-PSCs, respectively. The high compatibility between PM6 and PM1 promotes the formation of an alloy state within the active layer, which enhances molecular arrangement orderliness and crystallinity, and vertical structural phase distribution. The ternary LbL all-PSCs based on PM6:PM1/PY-IT exhibit a higher power conversion efficiency (PCE) of 18.10% and better stability compared to the binary LbL all-PSCs based on PM6/PY-IT with a PCE of 16.96%. The optimized ternary LbL all-PSCs retain over 82% of their initial PCE after 790 h of storage in a glovebox. This research demonstrates that the effective combination of dual-donor ternary strategy and the LbL strategy provides a feasible route for achieving high-performance all-PSCs through regulating the morphology of the active layer.