Hanjian Lai

Achieving efficient charge transport while maintaining low nonradiative energy loss remains a key challenge in the molecular design of small‐molecule acceptors (SMAs) for organic solar cells (OSCs). Herein, we report a stepwise molecular engineering strategy based on sulfur locking and chlorination to regulate intermolecular packing and excited‐state properties simultaneously. Sulfur locking modifies molecular conformation and intermolecular packing, leading to enhanced exciton diffusion and charge transport. Subsequent chlorination further strengthens intermolecular interactions through additional Cl···S contacts, resulting in tighter π–π stacking and improved crystalline ordering. Binary OSCs based on D18:Qx2Ph‐SCl achieve an efficiency of 20.0% with a high open‐circuit voltage ( V _OC ) of 0.951 V, while maintaining a low nonradiative energy loss of ∼0.19 eV. Owing to its intrinsically lower reorganization energy and weaker electron–phonon coupling than L8‐BO, Qx2Ph‐SCl further serves as an effective third component in ternary OSCs, reducing nonradiative recombination and increasing the V _OC . As a result, the ternary device delivers an efficiency of 21.3%. This work demonstrates that stepwise sulfur locking and chlorination provide an effective molecular design strategy for simultaneously optimizing charge transport and voltage loss in high‐performance OSCs.

Organic solar cells (OSCs) hold promise for building‐integrated and wearable photovoltaics, yet excessive H ‐aggregation of non‐fullerene acceptors (NFAs) quenches luminescence and lowers the photoluminescence quantum yield (PLQY), limiting further efficiency gains. Here, we introduce NTCl‐4F, a molecular H ‐aggregation mediator, into the D18:L8‐BO‐C ₄ binary system. Designed with an identical backbone to L8‐BO‐C ₄ but featuring a rotatable central core that induces steric hindrance (dihedral angle of 4.87° as revealed by single‐crystal diffraction), NTCl‐4F effectively suppresses H ‐aggregation while promoting ordered J ‐aggregation (with average fibril diameters from 20.75 to 17.16 nm). This aggregation‐mode modulation enhances the PLQY from 6.13% to 7.52%. Furthermore, the ordered J ‐aggregation induced by NTCl‐4F enhances the crystallinity of the system with increased crystal coherence lengths (CCL) and decreased fractal dimension ( D _f ), achieving synchronous improvement of short‐circuit current. Consequently, the NTCl‐4F‐modified device achieves a power conversion efficiency (PCE) of 20.8% under non‐annealed conditions, which stands among the highest reported efficiencies for non‐annealed OSCs. The strategy proves general, yielding efficiency improvements in PM6:Y6 and D18:Y7 systems. This work establishes aggregation‐mode engineering via an H ‐aggregation mediator as a versatile route to enhance PLQY and crystallinity for high‐performance OSCs.

Organic solar cells (OSCs) hold promise for building‐integrated and wearable photovoltaics, yet excessive H ‐aggregation of non‐fullerene acceptors (NFAs) quenches luminescence and lowers the photoluminescence quantum yield (PLQY), limiting further efficiency gains. Here, we introduce NTCl‐4F, a molecular H ‐aggregation mediator, into the D18:L8‐BO‐C ₄ binary system. Designed with an identical backbone to L8‐BO‐C ₄ but featuring a rotatable central core that induces steric hindrance (dihedral angle of 4.87° as revealed by single‐crystal diffraction), NTCl‐4F effectively suppresses H ‐aggregation while promoting ordered J ‐aggregation (with average fibril diameters from 20.75 to 17.16 nm). This aggregation‐mode modulation enhances the PLQY from 6.13% to 7.52%. Furthermore, the ordered J ‐aggregation induced by NTCl‐4F enhances the crystallinity of the system with increased crystal coherence lengths (CCL) and decreased fractal dimension ( D _f ), achieving synchronous improvement of short‐circuit current. Consequently, the NTCl‐4F‐modified device achieves a power conversion efficiency (PCE) of 20.8% under non‐annealed conditions, which stands among the highest reported efficiencies for non‐annealed OSCs. The strategy proves general, yielding efficiency improvements in PM6:Y6 and D18:Y7 systems. This work establishes aggregation‐mode engineering via an H ‐aggregation mediator as a versatile route to enhance PLQY and crystallinity for high‐performance OSCs.

Organic solar cells (OSCs) have achieved remarkable progress, yet improving exciton utilization in polymer donors remains challenging due to their intrinsically limited exciton diffusion length ( L _D ). Here, we report a donor‐selective templating strategy based on few‐layer‐like nickel–cobalt layered double hydroxide (NiCo‐LDH) nanosheets to regulate polymer donor assembly in OSCs. The hydroxyl‐rich NiCo‐LDH surface exhibits preferential affinity toward polymer donors and promotes ordered donor‐chain organization during film formation, while exerting limited influence on the acceptor component. This templating strategy enhances the molecular ordering of the donor phase and increases the L _D of D18 from 10.7 to 18.9 nm, accompanied by the formation of more ordered donor fibrillar structures. The coordinated improvements in donor organization and exciton transport are further associated with enhanced exciton‐to‐charge conversion, more balanced carrier transport, and suppressed recombination. Consequently, D18:L8‐BO‐based OSCs achieve a maximum power conversion efficiency (PCE) of 21.36%, independently certified at 21.09%, together with improved stability under continuous illumination. Analogous donor‐biased interactions, enhanced exciton diffusion, regulated fibrillar organization, and improved photovoltaic performance are also observed in PM6 and D18‐Cl systems. These results highlight the broader applicability of chemically active 2D templating for coordinating polymer donor assembly and exciton transport toward high‐performance OSCs.

Wide‐bandgap (WBG) perovskites with a ∼1.78 eV bandgap are essential for monolithic all‐perovskite tandem cells, yet their efficiency and stability are limited by complex precursor chemistry, uncontrolled crystallization, defect formation, and photoinduced halide segregation. Here, we report 4‐(3‐Carbamimidoylguanidino)benzoic acid hydrochloride (CGBA) as a precursor‐level regulator for Cs/formamidinium (CsFA)‐based Br‐rich WBG perovskites. Through dynamic associations with lead–halide species and organic cations, CGBA modifies the local precursor environment and alters the stage‐dependent film‐formation behavior during spin coating and annealing. This regulation moderates crystallization, promotes texture development, reduces trap‐mediated nonradiative recombination, and suppresses photoinduced halide segregation. Consequently, the optimized 1.78 eV single‐junction device achieves a power conversion efficiency (PCE) of 21.43% and a fill factor (FF) of 85.89%, placing it among the highest reported FF values for 1.75–1.79 eV single‐junction WBG perovskite solar cells. The strategy is also transferable across multiple compositions and conditions, yielding efficiencies of 27.32% (1.53 eV), 23.91% (1.68 eV), 18.75% (1.85 eV), and 26.08% (1.58 eV, antisolvent‐free). Unencapsulated target devices retain 93% of their initial efficiency after 4500 h in N ₂ . When integrated into a monolithic all‐perovskite tandem, the CGBA‐optimized WBG subcell enables a laboratory‐measured PCE of 29.63%. This work establishes precursor‐level regulation as a transferable strategy for efficient and stable WBG perovskites and all‐perovskite tandems.

All‐perovskite tandem solar cells promise to surpass the Shockley–Queisser limit, but the buried interface between the hole transport layer (HTL) and narrow‐bandgap (NBG) Pb–Sn perovskite suffers from non‑radiative recombination, energy mismatch, and defects. Here, we use 3‑amino‑4‑hydroxybenzenesulfonic acid (APS) as a multifunctional dipolar molecule to engineer this interface. The sulfonate group anchors onto the HTL, creating oriented dipoles that tailor the electrostatic field; amino and hydroxyl groups synergistically passivate traps, coordinate undercoordinated Pb ^{2 +} and Sn ^{2 +} , inhibit Sn ^{2 +} oxidation, and modulate crystallization. This optimizes energy alignment, establishes a type‑II band structure and ohmic contact, suppresses recombination, and promotes carrier transport. Consequently, the APS‑modified single‑junction NBG Pb–Sn cell achieves a power conversion efficiency (PCE) of 24.02%, versus 22.21% for the control, and shows improved stability (retaining 86% of initial PCE after 2600 h in N ₂ ). Applying the same strategy to all‑perovskite tandem cells yields a PCE of 29.51%. This work provides a dipole‑mediated interface design that simultaneously addresses defect passivation, energy‑level tuning, and charge extraction, offering a promising pathway toward high‑efficiency and durable Pb–Sn mixed perovskite solar cells and their tandem architectures.

Widebandgap (WBG) perovskites are critical for highefficiency tandem solar cells but suffer from rapid crystallization, photoinduced halide segregation, and interfacial losses. We introduce methyl 2(4,4,5,5tetramethyl1,3,2dioxaborolan2yl)1Hindole7carboxylate (MHIC) as a multifunctional modulator for 1.68 eV WBG perovskites. Its methoxycarbonyl and boronate groups form Lewis acid–base and hydrogenbonding interactions with the perovskite lattice, effectively passivating defects, reinforcing the framework, and suppressing halide segregation via lattice stabilization. Concurrently, MHIC creates a favorable interfacial dipole that lowers the holeextraction barrier, while retarding nucleation and crystal growth to yield largegrained, lowdisorder films. Singlejunction inverted cells achieve a champion efficiency of 23.80% with an outstanding fill factor of 86.27% and negligible hysteresis—among the best reported for this bandgap. The strategy is universally effective across compositions from 1.25 to 1.85 eV, including 1.58 eV without antisolvent. Integrated into monolithic twoterminal tandems with TOPCon silicon bottom cells, devices reach 32.04% (0.9025 cm ² ). Unencapsulated cells exhibit markedly improved operational stability, retaining 95.26% of initial efficiency after 4500 h storage in nitrogen. This work offers a holistic molecularengineering approach that simultaneously tailors crystallization kinetics, electronic structure, and phase stability, providing a viable route to overcome the persistent efficiency–stability tradeoff in WBG perovskite photovoltaics.

Organic solar cells are among the most advanced thin‐film photovoltaic technologies due to their lightweight, thin, and flexible characteristics. However, an inherent trade‐off between open‐circuit voltage ( V _OC ) and short‐circuit current density ( J _SC ) exists, fundamentally stemming from the balance between charge generation and recombination. To address this challenge, we developed a two‐dimensional extension molecule based on the A‐D‐A′‐D‐A non‐fullerene acceptor (NFA) framework by replacing the central core with anthracene and introducing halogen‐free end groups, yielding a novel molecule named QxAt. This molecule combines high crystallinity with a complementary absorption spectrum to commonly used NFAs. When incorporated as a voltage‐current balancer into the PM6:BTP‐eC9 system, the active layer morphology was largely preserved, while molecular packing was modestly optimized, contributing to more efficient exciton dissociation and charge collection, improved hole and electron mobilities, and effective suppression of charge recombination, ultimately enabling a moderate improvement in J _SC . More importantly, QxAt significantly increased the electroluminescence quantum efficiency, effectively suppressing non‐radiative recombination and reducing energy loss, which in turn elevated V _OC . Consequently, the PCE was markedly improved from 18.9% to 20.1%, achieving a synergistic optimization of both V _OC and J _SC . This work provides a molecular design strategy to mitigate the voltage‐current trade‐off for high‐efficiency organic photovoltaics.

Hard carbon (HC) is the leading anode candidate for sodium‐ion batteries, but its practical optimization remains constrained by an unresolved question: which structural motifs actually store Na ⁺ at low potential? Early voltage‐profile assignments separated sloping capacity from plateau capacity and attributed them to adsorption, intercalation, or pore filling. However, recent evidence indicates that these assignments are often sample‐dependent and may overinterpret individual characterization signatures. This Review re‐examines HC anodes from the perspective of site‐resolved Na storage. We first compare the evolution of sodium‐storage models and clarify what each model explains, where it fails, and why apparently contradictory conclusions have emerged. We then focus on the low‐voltage plateau, discussing monolayer Na accumulation, quasi‐metallic Na cluster formation, closed‐pore filling, and the remaining pore‐volume paradox. Particular attention is given to the strengths and limitations of WAXS/XRD, SAXS, XPS, Raman, NMR, titration, and theoretical simulations for assigning Na storage states. Finally, we connect mechanistic understanding to active‐site design, including defects, heteroatoms, pores, metal‐assisted motifs, and surface functional groups, emphasizing which design rules are established and which remain speculative. HC design must move beyond qualitative structure‐performance correlations toward quantitative active‐site identification, closed‐pore metrology, and full‐cell‐relevant optimization of plateau capacity, initial Coulombic efficiency, and scalability.

Molecular aggregation behavior of non‐fullerene acceptors (NFAs) plays a pivotal role in the photovoltaic performance of organic solar cells (OSCs). In Y‐series NFAs, excessive H‐like core contacts may increase packing disorder, while terminal group‐mediated J‐like interactions favor electronic coupling, luminescence, and reduced nonradiative loss. Controlling the H/J aggregation balance therefore remains a key challenge. Herein, three novel NFAs—C8C8, C8‐7R, and C8EH—featuring identical conjugated backbones but systematically varied inner alkyl chains were designed to finely modulate aggregation states. Theoretical calculations and single‐crystal analysis show that increased inner‐chain steric hindrance suppresses core‐involved contacts (H‐aggregation) while favoring terminal group‐mediated (J‐aggregation) interactions. Accordingly, C8EH exhibits the strongest J‐preferred packing tendency and enhanced molecular ordering, supported by compact terminal contacts, redshifted absorption, faster aggregation, and refined fibrillar morphology. When fabricated with the donor D18, C8EH‐based OSC devices delivered an outstanding power conversion efficiency (PCE) of 20.73%, representing one of the highest values reported for additive‐ and annealing‐free OSCs with higher current and reduced energy loss. This work demonstrates that inner‐chain steric modulation can promote J‐aggregated packing and ordered molecular organization, providing an effective strategy for high‐performance NFAs and process‐simplified OSCs.