All-perovskite tandem solar cells (TSCs) demonstrate exceptional potential to overcome the single-junction efficiency limit through enhanced photon harvesting across the solar spectrum and suppressed thermalization effects, achieving theoretical power conversion efficiencies surpassing 44%. Wide-bandgap perovskites solar cells (WBG PSCs) are crucial for tandem photovoltaics, and have witnessed exponential progress during the last decade. However, these devices suffer from severe open-circuit voltage (V_OC) deficits, primarily due to interfacial recombination and carrier transport losses. A major contributor to these losses is the uncontrolled formation of insulating two-dimensional (2D) perovskite phases during surface passivation. Here, we introduce 4-hydroxyphenylethyl ammonium iodide (p-OHPEAI) as a multifunctional molecular additive to address this critical trade-off. Unlike conventional phenethyl ammonium iodide (PEAI), which forms the insulating 2D phase and the invert electric field by vertical molecular orientation that impedes charge extraction, the hydroxyl group (–OH) in p-OHPEAI enables parallel molecular adsorption on perovskite surfaces via synergistic interactions between amino (–NH₃) and –OH groups. This configuration effectively eliminates the formation of insulating 2D perovskite phase, passivates undercoordinated halide and lead vacancies, reducing non-radiative recombination. Additionally, the polarity of p-OHPEAI generates a dipole moment at the perovskite/electron transport layer (ETL) interface, optimizing energy-level alignment and facilitating electron extraction. By incorporating p-OHPEAI into 1.77 eV WBG PSCs, we achieved a remarkable V_OC of 1.344 V, corresponding to a minimal voltage deficit of 0.426 V, which is among the lowest reported V_OC-deficit values for the inverted WBG PSCs with bandgaps ranging from 1.75 to 1.80 eV. The optimized device delivered a power conversion efficiency (PCE) of 19.24%, demonstrating superior performance compared to conventional PEAI-passivated cells. When integrated into all-perovskite TSCs, this strategy enabled a champion PCE of 28.50% (with a certified efficiency of 28.19%). Furthermore, the devices exhibited excellent operational stability, maintaining over 90% of their initial efficiency after 350 h of continuous illumination, highlighting the robustness of the hydroxyl-driven passivation approach. The introduction of hydroxyl groups in passivation molecules provides a versatile strategy to balance defect suppression and charge transport, bridging the gap between high voltage and efficient carrier extraction.

The design of high-performance small-molecule acceptors (SMAs) for organic solar cells (OSCs) remains a central challenge, particularly under the growing demand for environmentally friendly processing conditions. While halogenation has been widely employed to optimize electronic structures and molecular packing, its reliance on toxic halogenated solvents and the limited tunability of intermolecular interactions highlight the need for alternative strategies. In this context, core functionalization with cyano (CN) groups provides a unique opportunity, as the CN unit combines strong electron-withdrawing ability, high polarity, and linear geometry, potentially offering synergistic regulation of both optoelectronic properties and supramolecular assembly. However, systematic studies on core cyanation remain scarce, and its precise role in balancing charge transfer, molecular ordering, and energy loss in OSCs has not been thoroughly clarified.Here, we report a cyano-functionalized benzo[a]phenazine (BP)-core SMA, denoted as NA8, to explore how core cyanation influences device performance. The introduction of the CN group reduces the intramolecular charge transfer, resulting in a blue-shifted absorption and a slightly enlarged optical bandgap compared with the non-cyanated analogue NA1. Despite this apparent drawback, NA8 demonstrates superior molecular packing, as evidenced by grazing-incidence wide-angle X-ray scattering (GIWAXS) measurements showing a crystalline coherence length more than twice that of NA1 (101.3 Å vs. 44.6 Å). This improvement originates from the significantly enhanced dipole moment of NA8 (4.26 D vs. 2.21 D for NA1), which facilitates stronger electrostatic and noncovalent interactions (e.g., S···N and H···N contacts), thereby stabilizing more ordered packing motifs.At the blend-film level, atomic force microscopy (AFM) reveals that PM6:NA8 exhibits a rougher yet more clearly phase-separated morphology compared with PM6:NA1, providing continuous transport pathways. Photo-CELIV measurements confirm higher carrier mobility (2.36 × 10⁻⁴ cm² V⁻¹ s⁻¹ vs. 1.29 × 10⁻⁴ cm² V⁻¹ s⁻¹), while transient absorption spectroscopy shows faster exciton dissociation and reduced bimolecular recombination. Together, these synergistic effects explain why the PM6:NA8 device achieves an outstanding power conversion efficiency of 19.04% using non-halogenated o-xylene, compared with 15.14% for PM6:NA1. The improvement primarily arises from the significantly enhanced short-circuit current density (27.35 mA cm⁻²) and fill factor (78.3%), while the open-circuit voltage is only moderately reduced (0.889 V vs. 0.914 V) due to increased reorganization energy associated with C–C bond vibrations in the CN-substituted BP core. Our study identifies core cyanation as a powerful molecular engineering strategy to concurrently tune energy levels, strengthen molecular packing, and optimize nanoscale morphology, providing valuable design guidance for next-generation organic photovoltaics.

In the rapidly evolving field of photovoltaic technology, self-assembled monolayers (SAMs) have become essential hole-selective layers (HSLs) for inverted perovskite solar cells (PSCs). SAMs not only determine interfacial hole extraction but also significantly influence the film quality of the atop perovskite layers, consequently affecting the efficiency and stability of perovskite solar cells. Among various SAMs, carbazole-based SAMs, exemplified by 4PACZ, have emerged as prominent due to their electron-rich characteristics, making them some of the most prevalent HSLs in modern inverted PSCs. Nevertheless, 4PACZ exhibits significant limitations: one major issue is its limited molecular dipole, which leads to insufficient energy level alignment between the treated substrate and the perovskite, causing substantial interfacial energy loss. Another critical challenge is the flat structure of the carbazole unit, which often promotes molecular stacking, resulting in incomplete substrate coverage and non-uniform film formation, thereby compromising both device performance and stability. In this study, we designed a novel SAM based on a polycyclic aromatic hydrocarbon derivative, (4-(8H-dinaphtho[2,3-c: 2',3'-g]carbazol-8-yl)butyl)phosphonic acid (4PADNC), with the aim of optimizing hole transport in inverted PSCs. This SAM incorporates the structurally extended dinaphtho[2,3-c: 2',3'-g]carbazole (DNC) as the functional terminal group, replacing the single carbazole unit in the traditional material 4PACZ. The key structural difference is that the DNC group provides a significantly expanded π-conjugated skeleton and enhanced electron-rich characteristics. These features not only greatly enhance hole extraction and transport at the interface but also induce a significant increase in the molecular dipole moment, which is crucial for effectively adjusting the work function of ITO, ensuring proper alignment with the perovskite layer. Additionally, there is an intramolecular dihedral angle of approximately 34.62° in the DNC unit at the core of 4PADNC. This non-planar configuration contrasts sharply with the planar carbazole structure. The larger dihedral angle effectively suppresses excessive π-π stacking between molecules, which not only aids in forming a denser and more ordered molecular layer on the ITO surface but also provides a more favorable and defect-free substrate for the growth of the upper perovskite. With these upgrades, the inverted PSCs based on 4PADNC achieved a PCE as high as 24.32%, compared to 22.89% for the control devices based on 4PACZ. Furthermore, the 4PADNC-based devices also exhibited superior thermal stability and operational stability.

Organic solar cells (OSCs) have emerged as a core research direction in new energy materials due to their lightweight, flexibility, and solution-processability. Bulk heterojunction (BHJ)-based OSCs have achieved continuous performance breakthroughs with power conversion efficiency (PCE) exceeding 20% in recent years, laying a critical foundation for practical commercialization. However, device lifetime has become a key bottleneck restricting large-scale application: under long-term storage or photo-thermal aging conditions, the BHJ active layer suffers from performance degradation due to the instability of its nano-interpenetrating network morphology, mainly caused by the aggregation of small-molecule acceptors (SMAs) that form large-sized domains and structural defects, damaging charge transport channels. To address this stability challenge, the oligomerization modification strategy for SMAs has been proposed, yielding polymer and oligomer acceptors. While polymer acceptors improve active layer stability by increasing molecular weight, they suffer from broad molecular weight distribution and significant batch-to-batch differences due to fluctuating coupling efficiency, failing to meet large-scale preparation requirements. In contrast, oligomer acceptors (especially dimer acceptors with two repeating units) overcome these limitations with fixed molecular structures, simple synthesis without complex molecular weight regulation, minimized batch-to-batch deviations, and effective inhibition of small-molecule migration/aggregation, achieving a triple balance of stability, synthetic simplicity, and batch reproducibility. Additionally, dimer acceptors serve as ideal third components in binary active layers: they induce ordered π–π stacking via intermolecular non-covalent interactions, precisely regulate active layer crystal size to match exciton diffusion length, reduce charge transport losses, and compensate for binary systems' deficiencies in morphology regulation and performance stability. Currently, most reported dimer acceptors are based on fused-ring electron acceptors, featuring complex synthesis and high costs, while non-fused-ring electron acceptors offer simple design, few synthetic steps, and low cost via intramolecular non-covalent interactions (e.g., S…O, S…N interactions) and steric hindrance regulation. However, research on "non-fused-ring dimer acceptors" remains scarce, leaving a gap in combining non-fused-rings' low cost with dimers' lifetime and batch reproducibility advantages. To this end, this work designs and synthesizes a novel non-fused-ring dimer acceptor D-2BTH2F-H with simple preparation. The ternary OSCs based on D18:2BTH-2F: D-2BTH2F-H achieve a PCE of 17.95% and retain 80% of the initial efficiency after 1224 h of room-temperature storage, providing a new technical pathway for OSCs to balance low cost, high efficiency, long lifetime, and high batch reproducibility.

Double-cable conjugated polymers consist of a donor backbone and acceptor side chains linked by a long, flexible spacer. While this molecular design offers a promising solution to address the thermal instability and phase separation issues inherent in conventional binary blend systems, the development of high-performance double-cable polymers faces multiple significant challenges. The synthetic complexity is considerably high, requiring multi-step functionalization to attach the spacer to the acceptor unit, which often results in low yields and difficulties in purification. Moreover, the selection of suitable acceptor materials is severely limited, as only a narrow range of acceptors possess appropriate sites for spacer attachment while maintaining their intrinsic electronic properties. This limitation greatly restricts the exploration of material combinations and the potential for performance breakthroughs. Another critical yet underexplored challenge lies in the precise engineering of the spacer itself. Although studies have investigated the effect of spacer length, the role of spacer attachment position—a subtle but crucial structural parameter—remains poorly understood. This study designed and synthesized two such polymers, ZP-1 (with the spacer attached at the para-positions of the indenone benzene ring) and ZP-2 (at the ortho-positions), through spacer isomerization engineering. Investigations reveal that shifting the substitution from the ortho-(ZP-2) to the para-position (ZP-1) optimizes favorable molecular packing and enhances film crystallinity. This structural optimization facilitates exciton dissociation and charge transport, resulting in a significant improvement in the short-circuit current density and fill factor for ZP-1-based devices. Consequently, a power conversion efficiency (PCE) of 10.43% has been achieved, outperforming ZP-2 (9.44%). Furthermore, both polymers exhibit excellent thermal stability, retaining over 80% of their initial PCE after 8, 000 h of continuous thermal aging. Notably, when incorporated as a third component into the D18:BTP-eC9 binary blend, ZP-1 effectively optimizes the donor-acceptor interface, leading to a simultaneous enhancement in short-circuit current density (J_SC) and fill factor (FF) and a high PCE of 19.81%. This improvement is attributed to its templating effect during film formation and the promotion of charge generation at the optimized interface. The ternary device also demonstrates significantly enhanced thermal stability compared to the binary counterpart. This work provides valuable insights for the rational design of efficient and stable single-component organic solar cells, as well as novel ternary systems, by highlighting spacer isomerization engineering—specifically, the precise control of linkage position—as a powerful strategy to tailor molecular packing, crystallinity, and ultimate device performance.

Three isostructural Ti₆-oxo clusters with the formular of Ti₆O₄(PhPO₃)₂(L)₂(OⁱPr)₁₀, where L is 2-dimethylamine benzoate for Ti6-1, 3-dimethylamine benzoate for Ti6-2, and 4-dimethylamine benzoate for Ti6-3, were successfully synthesized and characterized. Thereinto, Ti6-3 displayed novel solvent dependent light absorption property. When dissolved in trifluoroethanol related solvent, evident visible light absorption was observed for Ti6-3, which was quite different from its absorption limited within the ultraviolate region in isopropanol related solvent. However, Ti6-1 and Ti6-2 displayed consistent absorption behavior in both of these solvents, respectively. It is worth noting that the solvent dependent absorption property remains quite rare for Ti-oxo cluster materials to date, although this has been commonly observed for organic conjugated materials. Nuclear magnetic resonance measurements revealed that the surface isopropoxide ligands on Ti6-3 were replaced by analogus trifluoroethoxide ligands on the cluster surface, resulting in Ti6-3-F. The solvatochromic effect was further illustrated by density functional theory calculation revealing the tuned energy levels between Ti6-3 and Ti6-3-F. Finally, Ti6-3-F was demonstrated able to serve as excellent cathode interlayer (CIL) in PM6:BO-4Cl and PM6:L8-BO based organic solar cells (OSCs), which achieved high efficiencies of 17.89% and 18.09%, respectively, suggesting its excellence as new CIL materials for high performance OSCs.