Ternary All‐Polymer Solar Cells with Efficiency up to 18.14% Employing a Two‐Step Sequential Deposition

Abstract 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 distribution and molecular ordering of the LbL‐type ternary all‐PSCs can be improved in comparison to the LbL‐type PM6/PY‐SSe‐V binary all‐PSCs. The formation of the superior bulk microstructure can not only promote charge transport and extraction properties but also reduce energetic disorder and non‐radiative recombination loss, thus improving all three photovoltaic parameters simultaneously. Consequently, the PM6/(PY‐SSe‐V:PY‐Cl) ternary all‐PSCs show the best efficiency of 18.14%, which is among the highest values reported to date for all‐PSCs. This work provides a facile and effective LbL‐type ternary strategy for obtaining high‐efficiency all‐PSCs.