Asymmetric Isomer Effects in Benzo[c ][1,2,5]thiadiazole‐Fused Nonacyclic Acceptors: Dielectric Constant and Molecular Crystallinity Control for Significant Photovoltaic Performance Enhancement

Abstract

Herein, asymmetric isomer effects are systematically explored by designing and synthesizing two benzo[c][1,2,5]thiadiazole (BT)‐fused nonacyclic electron acceptors. By changing from BP6T‐4F to asymmetric ABP6T‐4F, significantly enhanced dielectric constant and inhibited excessive molecular aggregation and unfavorable edge‐on orientation could be achieved. The reduced exciton binding energy also facilitates a more efficient dissociation process in PM6:ABP6T‐4F compared to PM6:BP6T‐4F with the same energy offset. Moreover, the weaker crystallization behavior enables a significantly enhanced miscibility between PM6 and ABP6T‐4F than that between PM6 and BP6T‐4F, which leads to an optimized micromorphology with smooth surface, suitable domain size, and ordered π–π stacking. Organic solar cells (OSCs) based on PM6:ABP6T‐4F achieve a 15.8% power conversion efficiency (PCE), which is remarkably higher than that of PM6:BP6T‐4F‐based OSCs (6.4%). Furthermore, ternary devices are also fabricated considering good compatibility between ABP6T‐4F and CH1007 to deliver a PCE over 17%. This study reveals the effectiveness and great potential of asymmetric isomerization strategy in regulating molecular properties, which will provide guidance for the future design of non‐fullerene acceptors.

15.71% Efficiency All‐Small‐Molecule Organic Solar Cells Based on Low‐Cost Synthesized Donor Molecules

“…The figure-of-merit (FOM) values, FOM = PCE/SC D:A [51][52][53] where PCE is power conversion efficiency and SC is the synthetic complexity of donors and acceptors, can be considered as a rough but reasonable tool for evaluating the accessibility of photovoltaic materials used in possible OSC applications. The value of FOM represents the cost-efficiency balance of each given donor material photovoltaic system.…”

Review on Y6-Based Semiconductor Materials and Their Future Development via Machine Learning

“…Blended with PM6, the PCEs of BP4T-4F, BP5T-4F, and ABPT-4F are 17.1% [73], 16.7% [73], and 15.2% [73], respectively. Gao and coworkers [74] also tried to fuse six thiophene units into the Y6 core and constructed a new acceptor BP6T-4F. In addition, another isomer molecule of BP6T-4F, namely, ABP6T-4F, was synthesized based on the isomerization of asymmetric strategy.…”

“…In Figure 6d,e, the diffraction signal in ABP6T-4F shows a stronger signal in the qr direction (stronger 𝜋-𝜋 stacking property) even though the signal is weaker in the qz direction (weaker crystallization property). The advantages of the symmetry-breaking strategy in this molecule far outweigh the disadvantages, thus resulting in a significantly improved efficiency of ABP6T-4F (15.8% [74]) than that of BP6T-4F (6.4% [74]). Li and coworkers [22] by 2021 have created L8-R (L8-BO, L8-HD, and L8-OD) acceptors through a branched-chain in R 1 .…”

Near‐Infrared Absorbing Nonfullerene Acceptors for Organic Solar Cells

“…Moreover, larger dipole moment will also increase the dielectric constant and thus decrease the exciton binding energy to improve dissociation efficiency and reduce the energy loss of OSCs. [45,46] To design highperformance NIR NFAs, a combined strategy with more than one mentioned above should be required.…”

“…[56] Another example of asymmetrically altering π-core conjugation using thiophene, dithieno[3,2-b:2 0 ,3 0 -d]thiophene and thieno[2 0 ,3 0 :4,5]thieno [3,2b]thieno [2,3-d]thiophene units to replace TT unit in Y6 core provided a series of Y6 analogs (AY6, BP5T-4F, ABP4T-4F, BP6T-4F, and ABP6T-4F, Figure 5) with different sizes of cores and molecular conformations, which further provides insights into the molecular structure-property-performance relationship of Y6type NFAs. [45,46,57]…”