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Although non‐fused ring electron acceptors (NFREAs) have received increasing attention due to their relatively low synthetic costs, the achievement of high efficiencies strongly depends on tedious pre‐ or/and post‐treatments to refine the active layers, which in turn greatly increase fabrication complexity and expense of organic solar cells (OSCs). Nowadays most of the available as‐cast devices based on NFREAs are below 12% efficiencies. Herein, phenylalkyl category side groups (CnPh) are employed to construct new NFREAs named BOR‐CnPh (n = 3, 4, and 6), which exhibit inherently decent molecular aggregation and thus exclude additional treatments from device fabrication. The modified alkyl spacers of CnPh side groups not only trigger different aggregation of the acceptors, but also regulate the interaction conformations of donor (D) and acceptor (A), and thus D/A interactions. Encouragingly, the pristine PBDB‐T:BOR‐C4Ph blend delivers intrinsic fibrous networks with dominating face‐on orientation, which yields an optimal efficiency up to 13.12%, and ranks as the highest value among as‐cast OSCs based on NFREAs. This research provides a practical strategy to control molecular aggregations, interactions, and pristine heterojunction morphologies for easily available and high‐performance organic photovoltaics. [ABSTRACT FROM AUTHOR]

Efficient organic solar cells (OSCs) equipped with thick‐film active layers and high flexibility are of great significance for industrial preparation and practical applications. Herein, a ternary strategy coupled with a functional additive is employed to obtain efficient thick‐film flexible OSCs. A novel polymer donor PBB1‐F with good planarity is synthesized as a third component to optimize photon capture and molecular stacking. Meanwhile, a high dielectric constant polyarene ether (PAE) functional additive with strong adhesion not only greatly improves exciton dissociation efficiency, but also acts as locking cage‐like for effective enhancement of the mechanical stability of active layer. As a result, the PM6:PBB1‐F:Y6‐BO‐4Cl and PM6:PBB1‐F:BTP‐eC9 based ternary OSCs with PAE exhibit an efficiency of 17.91% and 18.51% under rigid thin‐film state, and perform better under thick‐film state of rigid (16.40% and 16.84%) and flexible (14.78% and 14.95%). Under the protection of the polymers, tight entanglement and cage‐like PAE adhesion, the elongation at break of the active layer increases by more than fourfold (27.3%), and gives a super flexible thick‐film OSCs that maintains more than 90% performance after 1000 bending cycles with a diameter of 10 mm. Overall, this work provides a new feasible scheme to effectively solve thickness sensitivity and flexibility issues in the context organic photovoltaic applications. [ABSTRACT FROM AUTHOR]

The morphology of the active layer plays a crucial role in the device performance and stability of organic solar cells (OSCs). To obtain the optimized blend film morphology, numerous solvent additives have been developed and utilized. Nevertheless, the commonly used high boiling point solvent additives have strict volume control and residual problems, which are not conducive to the development of OSCs. To alter the situation, it is urgent to develop highly volatile additives to minimize the unfavorable effect. Here, a volatile aromatic small molecule, benzoylacetate (BA), is used as a solid additive to control the morphology of the active layer during the post-treatment procedure. More importantly, BA has an apparent positive interaction with Y6, leading to more favorable molecular arrangement in the blend film and enhanced charge transfer properties. Finally, the BA-treated PM6:Y6 device exhibits improved device performance and photostability. Moreover, BA could be used as a universal solid additive for different OSC systems. Specifically, a superior PCE of 18.5 % is achieved in BA-processed PM6:L8-BO binary system with good photostability. Our work demonstrates an approach of applying a volatile solid additive to improve the device performance and photostability. [Display omitted] • High-performance organic solar cells (OSCs) were fabricated by introducing benzoylacetone (BA), a volatile aromatic small molecule, into the non-fullerene acceptor (NFA) systems. • The addition of BA can be used to control the blend morphology and obtain improved crystallinity and appropriate phase separation. Meanwhile, good volatility of BA is beneficial to improve the photostability of OSCs. • For the binary PM6:L8-BO device, a notable PCE of 18.5 % was yielded after treatment with the BA additive, which is much higher than that of the device treated with DIO. [ABSTRACT FROM AUTHOR]