Layer‐by‐Layer‐Processed Ternary All‐Polymer Organic Solar Cells with 17.74% Efficiency Enabled by Introducing a Designed Narrow‐Bandgap Guest Polymer Acceptor

Obtaining an admirably modified vertical phase separation of the active layer for all‐polymer solar cells (all‐PSCs) to facilitate charge generation, charge transfer and transport properties are a prerequisite for achieving high performance. Herein, the active layer of all‐PSCs is finely manipulated by combining a ternary blend strategy with a layer‐by‐layer (LbL) process. Based on the LbL‐processed PM6/PYT‐1S1Se host binary all‐PSCs, a chlorinated polymer acceptor PYT‐1S1Se‐4Cl is designed and introduced into the host system for rationally controlling blend morphology with ordered molecular stacking and suitable vertical distribution. The optimized bulk microstructure of the ternary system is not only beneficial to the charge generation and charge transport properties, but also can significantly reduce the nonradiative energy loss that occurs in the LbL‐type ternary blend. Thus, the LbL‐type PM6/(PYT‐1S1Se:PYT‐1S1Se‐4Cl) ternary all‐PSCs exhibit a promising power conversion efficiency (PCE) of 17.74%, which is higher than the corresponding binary systems (PCE = 16.86% for PM6/PYT‐1S1Se and PCE = 15.83% for PM6/PYT‐1S1Se‐4Cl), indicating the special merits of material design and processing technology. Overall, a promising combinatorial method for the morphological regulation of all‐polymer systems is demonstrated that contributes to enhanced efficiency.