Search

The molecular ordering and pre‐aggregation of photovoltaic materials in solution can significantly affect the nanoscale morphology in solid photoactive layers, and play a vital role in determining the power conversion efficiency (PCE) of organic solar cells (OSCs). Herein, a cold‐aging strategy is reported to mediate the pre‐aggregation of PM6 polymer in solution through a disorder‐order transition, which leads to dense and fine PM6 aggregates with enhanced π−π stacking in its blend thin films with either fused‐ring and non‐fused‐ring non‐fullerene acceptors (NFAs) including Y6‐BO, N3, IT‐4F, and PTIC. The fine aggregates of PM6 and slightly enlarged NFA domains improve the continuous networks with enhanced and balanced charge mobility. The resulting OSCs all demonstrate enhanced PCEs compared to their counterparts without any cold‐aging treatments, with PM6:Y6‐BO OSC being most effective from 16.6% to 17.7%, demonstrating the universality of this approach. This can be further optimized upon casting of the cold‐aging solution with the presence of solvent vapor, resulting in a champion PCE of 18.0% for PM6:Y6‐BO OSC, which is the highest PCE of this OSC reported in the literature. This work provides a rational guide for optimizing non‐fullerene OSCs via aggregation control before and during the solution casting process. [ABSTRACT FROM AUTHOR]

Despite the remarkable progress achieved in recent years, organic photovoltaics (OPVs) still need work to approach the delicate balance between efficiency, stability, and cost. Herein, two fully non‐fused electron acceptors, PTB4F and PTB4Cl, are developed via a two‐step synthesis from single aromatic units. The introduction of a two‐dimensional chain and halogenated terminals for these non‐fused acceptors plays a synergistic role in optimizing their solid stacking and orientation, thus promoting an elongated exciton lifetime and fast charge‐transfer rate in bulk heterojunction blends. As a result, PTB4Cl, upon blending with PBDB‐TF polymer, has enabled single‐junction OPVs with power conversion efficiencies of 12.76 %, representing the highest values among the reported fully unfused electron acceptors so far. [ABSTRACT FROM AUTHOR]

Efficient exciton dissociation at low energy offsets is key to overcoming voltage losses in organic solar cells. In this work, we developed two dimeric acceptors, i‐YT and o‐YT, by precisely controlling the position of an asymmetric electron‐donating linker. It induced the foldamer conformation of i‐YT with a para linkage (relative to the dicyano groups), while retaining the unfold conformation for o‐YT. This subtle structural modification influenced the molecular assembly properties, enabled near‐zero energy offset exciton dissociation and power conversion efficiencies exceeding 18 % for i‐YT based organic solar cells. Detailed excitonic dynamics further revealed that the linker position critically influences three processes: the formation of delocalized singlet excited states, ultrafast charge transfer (~5 ps) in solid blends, and the suppression of exciton recombination. Additionally, devices based on i‐YT demonstrated outstanding long‐term stability, retaining 85 % of their initial efficiency after 1,400 hours of continuous illumination. These findings introduce a new class of dimeric acceptors that combine high efficiency with exceptional stability, offering a promising pathway toward low‐energy‐loss organic photovoltaics. [ABSTRACT FROM AUTHOR]

Although encouraging progress in spin‐coated small‐area organic solar cells (OSCs), reducing efficiency loss caused by differences in film uniformity and morphology when up‐scaled to large‐area modules through meniscus‐guided coating is an important but unsolved issue. In this work, in‐depth research is conducted on the influence of both liquid and solid additives on the film uniformity and morphology of active layer in blade‐coated PM6:L8‐BO binary system. The study reveals that high boiling point liquid additives like 1,8‐diiodooctane (DIO) used in blade‐coating not only delay the volatilization of the solvent but also trigger the Marangoni flow in the same direction as capillary flow, causing excessive aggregation of acceptors, therefore destroying device performance. On the contrary, the solid additive 2‐Iododiphenyl ether (IDPE), which is first reported in this work, can preserve the mechanism for improving device performance while effectively suppressing the excessive aggregation of acceptors during the film‐forming process in blade‐coating from halogen‐free solvent of toluene, resulting in highly homogeneous large‐area active layer films. Consequently, organic solar modules with an impressive efficiency of 15.34% with a total module area of 18.90 cm2 via blade‐coating based on PM6:L8‐BO are achieved. This study not only provides a deep understanding on the effect of liquid and solid additives during blade‐coating from the perspective of fluid mechanisms but also gives a pathway for the development of green solvent printed high‐efficiency OSCs. [ABSTRACT FROM AUTHOR]

Charge events across organic–metal oxide heterointerfaces routinely occur in organic electronics, yet strongly influence their overall performance and stability. They become even more complicated and challenging for the heterojunction conditions in polymer solar cells (PSCs), especially when nonfullerene acceptors with varied energetics are employed. In this work, an effective interfacial strategy that utilizes novel small molecule self‐assembled monolayers (SAMs) is developed to improve the electronic and electric, as well as chemical properties of organic–zinc oxide (ZnO) interfaces for nonfullerene PSCs. It is revealed that the tailored SAMs with well‐controlled energy levels and molecular dipoles can effectively optimize the energetic barrier and work function (WF) of heterointerface for optimal electron extraction. In addition, the introduction of SAMs atop of ZnO facilitates not only acceptor segregation near the n‐contact interface, but also passivation of the photocatalytic activities for ZnO, to improve overall performance and photo stability of the derived nonfullerene PSCs. Overall, the methodology and structure–property relationship revealed herein would be beneficial for a wide range of hybrid electronics. [ABSTRACT FROM AUTHOR]