Understanding the Role of Removable Solid Additives: Selective Interaction Contributes to Vertical Component Distributions

Sequentially deposited organic solar cells (SD‐OSCs) have attracted great attention owing to their ability in achieving a more favorable, vertically phase‐separated morphology to avoid the accumulation of counter charges at absorber/transporting layer interfaces. However, the processing of SD‐OSCs is still quite challenging in preventing the penetration of small‐molecule acceptors into the polymer donor layer via erosion or swelling. Herein, solid additives (SAs) with varied electrostatic potential distributions and steric hinderance are introduced into SD‐OSCs to investigate the effect of evaporation dynamics and selective interaction on vertical component distribution. Multiple modelings indicate that the π–π interaction dominates the interactions between aromatic SAs and active layer components. Among them, p‐dibromobenzene shows a stronger interaction with the donor while 2‐chloronaphthalene (2‐CN) interacts more preferably with acceptor. Combining the depth‐dependent morphological study aided by multiple X‐ray scattering methods, it is concluded that the evaporation of SAs can drive the stronger‐interaction component upward to the surface, while having minor impact on the overall molecular packing. Ultimately, the 2‐CN‐treated devices with reduced acceptor concentration at the bottom surface deliver a high power conversion efficiency of 19.2%, demonstrating the effectiveness of applying selective interactions to improve the vertical morphology of OSCs by using SAs with proper structure. Solid additives with varied electrostatic potential and steric hinderance are introduced to investigate the impact of both evaporation dynamics and selective interaction on vertical component distribution. The removal of solid additives can drive the more strongly interacting component upward to the surface, delivering a high performance of 19.2%, among the highest efficiencies achieved in organic solar cells.