Xin Zhang

This work establishes a core-appended steric engineering to address the critical challenge of non-radiative recombination energy loss in organic solar cells through precisely regulating local conformation and intermolecular interactions.

The realization of high–efficiency as–cast organic solar cells (OSCs) represents a key step toward simplified processing and scalable fabrication for commercialization. However, achieving high–performance as–cast devices remains challenging because it demands delicate balance between donor–acceptor self–aggregation and miscibility. Herein, we fabricate as–cast OSCs through Flory–Huggins parameter (χ) engineering that precisely regulates donor–acceptor miscibility during solution casting. The chloroform–carbon disulfide (CF:CS ₂ ) mixed solvent, with tailored solubility and evaporation kinetics, dynamically modulates χ to form an optimized bulk heterojunction featuring desirable phase separation and a well–balanced fibrillar network. This design affords efficient exciton dissociation, facilitated charge transport, and suppressed recombination in the blend. Consequently, as–cast D18:L8–BO device processed with the CF:CS ₂ solvent system attained a PCE of 20.11% (certified as 19.69%) alongside enhanced photostability, representing the highest efficiency reported for as–cast devices. Besides, high PCEs of 18.89% and 15.12% are achieved in thick–film (300 nm) and large–area (20.17 cm ² ) as–cast devices. Moreover, a quantitative correlation between PCE and the interaction parameter χ is established, providing a quantitative guide for narrowing the miscibility window and identifying the optimal composition. These findings validate the efficacy of χ–parameter–mediated miscibility engineering in regulating blend phase behavior and provide a framework for advancing efficient as–cast OSCs.

As core processes determining the power conversion efficiency (PCE) of organic solar cells (OSCs), exciton dissociation and charge transfer are fundamentally restricted by the low intrinsic dielectric constant of organic semiconductors. Herein, two dielectric regulators (Drs) named Dr-1 and Dr-2 are judiciously designed with different molecular dipole moments to conduct research on dielectric engineering. The incorporation of S···F noncovalent conformational locks (NoCLs) endows Dr-2 with an extended π-conjugated backbone, improved molecular polarizability, reinforced charge delocalization and a larger dipole moment than Dr-1. Thus, Dr-2-modified OSCs based on the D18:L8-BO system achieve a PCE of 20.85%, surpassing the 20.13% of Dr-1-treated counterparts. Enhanced efficiencies across diverse donor-acceptor systems confirm the universal applicability of this strategy. Furthermore, 300 nm-thick OSCs incorporated with Dr-2 deliver a record-high PCE of 19.56%. This work provides a strategy for designing high-performance dielectric regulators via tuning molecular dipole moment and planarity simultaneously, thereby achieving high-efficiency OSCs.

The design of interlayer materials featuring precisely matched electronic properties with the active layer materials and robust thickness tolerance is crucial for advancing organic solar cell (OSC) performance and commercialization. Zwitterionic polymers have been investigated extensively as interlayer materials in organic electronics. However, sulfobetaine (SB) has been the most widely adopted zwitterionic chains, while other cation–anion combinations remain largely unexplored, and the contribution of the anionic groups in zwitterions is still a mystery. Here, we explored a bioinspired zwitterionic interlayer material, engineered through the synergistic integration of fluorinated phosphatidylcholine-based polar side chains and an acceptor–acceptor (A1–A2) conjugated backbone. Such a synchronous side chain/backbone “surgery” simultaneously achieves deep frontier molecular orbital energy levels aligned with state-of-the-art electron acceptors, suppressed parasitic absorption, highly ordered molecular packing, and reduced hydrophilicity. The resulting interlayer material, PDITz-PC, demonstrates strong work function modification, superior electrical properties, and excellent interfacial contact. In OSCs, PDITz-PC enables impressive power conversion efficiencies (PCEs) for both small area (0.04 cm2) and large area (0.6 cm2) devices across various active layer systems, accompanied by significantly improved operational device stability, attributed to enhanced exciton dissociation, improved charge transport, and suppressed charge recombination. Notably, PDITz-PC exhibits good thickness tolerance, solar cells retaining 92% of the peak PCE even at an interlayer thickness of 115 nm. This work highlights the critical need to synchronize interlayer design with advancements in active-layer materials via the harmonized engineering of side chains and backbones, offering a strategic route to achieving high-performance, durable, and scalable organic photovoltaics.

Organic solar cells (OSCs) advancement hinges critically on cathode interlayer materials (CIMs) that meet multiple requirements: thickness‐insensitivity to facilitate device upscaling, mitigated hydrophilicity to enhance stability, and processability from green solvents to minimize environmental impact and reduce post‐processing costs. We design and synthesize bis‐sulfonimide‐functionalized fulleropyrrolidine derivatives grafted with nonionic sidechains. C60‐BSI‐PS, incorporating phosphonate ester sidechains, exhibits superior electronic properties compared to its carbonate‐ester counterpart and outperforms benchmark fulleropyrrolidine with ionic sidechains. These characteristics promote efficient charge‐transport and suppress recombination even under thick‐film conditions. The phosphonate ester groups also endow C60‐BSI‐PS with high solubility in ethanol, eliminating the need for toxic halogenated solvents or methanol. When processed from ethanol, the C60‐BSI‐PS interlayer delivers a power conversion efficiency (PCE) of 19.76% in PM6:D18:L8‐BO‐based OSCs, alongside excellent operational stability. It retains >94% of its optimal PCE even at an ultra‐thick coating of 81 nm. The broad applicability of C60‐BSI‐PS is further demonstrated across leading binary, ternary, and quaternary OSC systems, achieving PCEs 21.11% for small‐area devices (0.04 cm ² ) and 19.69% for large‐area devices (0.6 cm ² ) in D18:L8‐BO:BTP‐eC9‐based system. Thus, engineering fullerene‐based materials through judicious sidechain functionalization is a powerful strategy for creating high‐performance, sustainable interlayers, paving the way for next‐generation photovoltaic technologies.

Organic solar cells (OSCs) advancement hinges critically on cathode interlayer materials (CIMs) that meet multiple requirements: thickness‐insensitivity to facilitate device upscaling, mitigated hydrophilicity to enhance stability, and processability from green solvents to minimize environmental impact and reduce post‐processing costs. We design and synthesize bis‐sulfonimide‐functionalized fulleropyrrolidine derivatives grafted with nonionic sidechains. C60‐BSI‐PS, incorporating phosphonate ester sidechains, exhibits superior electronic properties compared to its carbonate‐ester counterpart and outperforms benchmark fulleropyrrolidine with ionic sidechains. These characteristics promote efficient charge‐transport and suppress recombination even under thick‐film conditions. The phosphonate ester groups also endow C60‐BSI‐PS with high solubility in ethanol, eliminating the need for toxic halogenated solvents or methanol. When processed from ethanol, the C60‐BSI‐PS interlayer delivers a power conversion efficiency (PCE) of 19.76% in PM6:D18:L8‐BO‐based OSCs, alongside excellent operational stability. It retains >94% of its optimal PCE even at an ultra‐thick coating of 81 nm. The broad applicability of C60‐BSI‐PS is further demonstrated across leading binary, ternary, and quaternary OSC systems, achieving PCEs 21.11% for small‐area devices (0.04 cm ² ) and 19.69% for large‐area devices (0.6 cm ² ) in D18:L8‐BO:BTP‐eC9‐based system. Thus, engineering fullerene‐based materials through judicious sidechain functionalization is a powerful strategy for creating high‐performance, sustainable interlayers, paving the way for next‐generation photovoltaic technologies.

The commercial viability of organic solar cells (OSCs) is hindered by the trade-off between cost and performance. In particular, low-cost non-fused-ring electron acceptors (NFREAs) suffer from conformational disorder, limiting their photovoltaic performance. Herein, we strategically regulate conformational entropy (Sconf.) of NFREAs through the rational combination of intramolecular noncovalent interactions (INIs). The optimal candidate 3TT-SeS, identified through comprehensive density functional theory calculations, exhibits balanced Se···N and S···O INIs and demonstrates a significant reduction in Sconf. This strategy enables an exclusive single stable conformation and highly ordered molecular packing, thereby facilitating efficient charge transport. Consequently, the 3TT-SeS-based OSC achieved an outstanding power conversion efficiency of 19.26% (certified at 18.75%), setting a new benchmark for NFREA-based systems to date. More importantly, 3TT-SeS-based device demonstrates exceptional economic potential with an extremely low power generation cost of 0.77$ kW−1, much lower than several high-performance FREA-based systems. Our work demonstrates a low-Sconf. design of NFREAs for cost-effective and high-performance organic photovoltaics.

The advancement of acceptor-donor-acceptor (A-D-A)-type nonfullerene acceptors (NFAs) has significantly enhanced the near-infrared organic photodetector (NIR OPD) performance. However, structural instability arising from vulnerable exocyclic vinyl bridges between donor (D) and acceptor (A) units remains a critical challenge for both material and device durability. Herein, we break this bottleneck through a pioneering terminal engineering strategy and present the judicious design and synthesis of novel electron-withdrawing 2-(2-bromo-3-cyano-8H-indeno[2,1-b]thiophen-8-ylidene)malononitrile (ITC2H) toward exocyclic-vinyl-free NFAs. Compared with the classical NFA (BTP-IC2H), the ITC2H-flanked derivative BTP-ITC2H exhibits not only enhanced chemical/photostability but also improved crystallinity, broadened and red-shifted absorption spectrum, optimized miscibility with polymer donor, and reduced reorganization energy. These synergistic advantages yield an optimized nanomorphology with suppressed trap states and favorable charge transport dynamics. The resulting self-powered OPD achieves a dark current density (J_d) of 3.3 × 10^-11 A cm^-2 and noise-limited specific detectivity (D*_sh) surpassing 10¹³ Jones across 310-910 nm, coupled with a linear dynamic range (LDR) of 141 dB and superior thermal stability. The generality of this design paradigm is demonstrated by extending ITC2H to its halogenated analogues, enabling response extension to 1300 nm with a J_d of 3.87 × 10^-11 A cm^-2 and D*_sh approaching 10¹³ Jones even at 1200 nm, underscoring their versatility for diverse applications. The molecular engineering paradigm in this work provides critical insights into structure-stability-performance relationships, advancing the development of robust and efficient organic optoelectronics for practical implementation.

Molecular conformation is a critical structural attribute of organic molecules and polymers in addition to their constitution and configuration, thereby forming the foundation for understanding macroscopic material properties and device functionality. For nonfused‐ring electron acceptors (NFREAs) featuring multiple σ‐bonds with high rotational degrees of freedom, significant challenges remain in precisely regulating molecular conformation, particularly in modulating the syn ‐ and anti ‐conformation preferences. Here, we demonstrate precise engineering of NFREAs through conformation‐directed molecular design, achieving a syn ‐to‐ anti ‐conformational transition via utilizing intramolecular noncovalent S···F interactions. This conformational regulation strategy enables a systematic investigation of how syn ‐/ anti ‐conformational preferences influence molecular planarity and rigidity, self‐assembly behavior, charge transport properties, and device performance. Our results reveal that the anti ‐conformation endows anti ‐TT‐F with enhanced crystallinity, reduced reorganization energy, and improved charge carrier mobility compared to its syn ‐conformational counterpart. Consequently, binary and ternary devices based on anti ‐TT‐F achieve remarkable power conversion efficiencies of 15.08% and 19.88%, respectively. This conformational engineering strategy unveils a previously overlooked dimension in molecular design, providing fundamental guidelines for developing high‐performance organic solar cells through the rational manipulation of conformational landscapes.

Molecular conformation is a critical structural attribute of organic molecules and polymers in addition to their constitution and configuration, thereby forming the foundation for understanding macroscopic material properties and device functionality. For nonfused‐ring electron acceptors (NFREAs) featuring multiple σ‐bonds with high rotational degrees of freedom, significant challenges remain in precisely regulating molecular conformation, particularly in modulating the syn ‐ and anti ‐conformation preferences. Here, we demonstrate precise engineering of NFREAs through conformation‐directed molecular design, achieving a syn ‐to‐ anti ‐conformational transition via utilizing intramolecular noncovalent S···F interactions. This conformational regulation strategy enables a systematic investigation of how syn ‐/ anti ‐conformational preferences influence molecular planarity and rigidity, self‐assembly behavior, charge transport properties, and device performance. Our results reveal that the anti ‐conformation endows anti ‐TT‐F with enhanced crystallinity, reduced reorganization energy, and improved charge carrier mobility compared to its syn ‐conformational counterpart. Consequently, binary and ternary devices based on anti ‐TT‐F achieve remarkable power conversion efficiencies of 15.08% and 19.88%, respectively. This conformational engineering strategy unveils a previously overlooked dimension in molecular design, providing fundamental guidelines for developing high‐performance organic solar cells through the rational manipulation of conformational landscapes.