efficiencies (PCEs) of the state-of-theart all-PSCs have reached over 16-18% currently, [2] mainly resulting from the recent development of the polymerized small molecule acceptors (PSMAs). [1e,2b,eg] Nonetheless, the PCE of the all-PSCs still lags behind that (over 19%) of the SMA-based PSCs, [3] because of the lack of narrower bandgap P A s and the relative difficulty in finely tuning blend morphology of all-polymer systems. [1e,4] Encouraged by the development of the A-DA′D-A structured Y-series SMAs, [3a,5] several research groups reported narrow bandgap n-type PSMAs based on Y-series derivatives and increased PCEs of the all-PSCs to ≈13−17%. [2e,6] For instance, Jia et al. and Wang et al. first designed and synthesized Y5-based PSMAs PJ1 and PYT with thiophene as π-bridge, which achieved high PCEs of 14.4% and 13.4% by using polymer donors PBDB-T and PM6 in 2020. [6a,7] However, these Y5-based PSMAs as well as their derivatives are generally limited by their optical bandgaps (E opt g , E opt g values of 1.43-1.45 eV from the onset of the absorption profiles), [6b,7,8] leading to the limited photocurrent and efficiency improvement. Subsequently, Yu et al. and our group synthesized PSMAs PYF-T-o [9] and PY2F-T [2f ] containing a Y5 framework modified by fluorine atoms, which exhibited the narrower E opt g values of ≈1.38 eV and higher PCEs of over 15% achieved in relevant all-PSCs. In addition, Fu et al. and our group used benzotriazole as the central core to develop PSMAs PZT-γ [10] and PYT-Tz, [11] which possess red-shifted absorption and upshifted energy levels in comparison to PYT, thereby enhancing the short-circuit current density (J SC ) and PCE of the device. Subsequently, Fu and his coworkers further developed PSMAs with a selenophene-fused Y5 framework and halogenated end groups. [2g,12] Selenium and fluorine/chlorine substitutions have synergistic effects in broadening absorption and enhancing intermolecular interactions, resulting in red-shifted absorption (E opt g values of 1.37-1.40 eV) compared to other Y5-based PSMAs and better active layer morphology when blended with PM6. [2g,12b] Besides, in comparison to the thiophene linkerbased P A s PJ1 and PYT, the vinylene-based PSMA PY-V-γ demonstrates a slightly narrower E opt g of 1.41 eV and a better conjugation and tighter interchain stacking, resulting in more suitable phase segregation in the PY-V-γ blend with an improved PCE of 17.1%. [13] Therefore, developing high-performance P A s Achieving a finely tuned active layer morphology with a suitable vertical phase to facilitate both charge generation and charge transport has long been the main goal for pursuing the highly efficient bulk heterojunction all-polymer solar cells (all-PSCs). Herein, a solution to address the above challenge via synergistically combining the ternary blend strategy and the layer-by-layer (LbL) procedure is proposed. By introducing a synthesized polymer acceptor (P A ), PY-Cl, with higher crystallinity into the designed host acceptor PY-SSe-V, vertical phase...