Aggregation Engineering of Toluene‐Processed Acceptor Layer Enables Over 19% Efficiency of Air‐Blade‐Coated Organic Solar Cells

Abstract Understanding the unique features of photovoltaic materials in high‐performance blade‐coated organic solar cells (OSCs) is critical to narrow the device performance difference between spin‐coating and blade‐coating methods. In this work, it is clarified that the molecular packing of acceptor and molecule‐solvent interaction plays an essential role in determining the photovoltaic performance of blade‐coated layer‐by‐layer OSCs. It is demonstrated that the unique dimer packing feature of L8‐BO‐4Cl can lead to lower excited energy (∆ E S1 ) and dominant J ‐aggregates in the blade‐coated film compared to the analogs of Y6 and L8‐BO. Meanwhile, the weaker molecule‐solvent interaction between L8‐BO‐4Cl and toluene is in favor of forming prominent J ‐aggregation in blade‐coated film, contributing to a more compact π‐stacking than Y6 and L8‐BO. Additionally, the blade‐coated D18/L8‐BO‐4Cl film shows more defined interpenetrating networks with clearer donor‐acceptor interfaces than D18/Y6 and D18/L8‐BO, facilitating improved charge extraction and suppressed charge recombination. As a result, the air‐blade‐coated layer‐by‐layer device based on D18/L8‐BO‐4Cl yields a remarkable power‐conversion efficiency (PCE) of 19.31% without any additive and post‐treatment, while much lower PCEs of 7.01% and 16.47% are obtained in the device based on D18/Y6 and D18/L8‐BO, respectively. This work offers an effective approach to developing highly efficient air‐blade‐coated layer‐by‐layer OSCs.