Non-radiative recombination losses in non-fullerene acceptors (NFAs) represent a critical bottleneck limiting the open-circuit voltage (Voc) and power conversion efficiency (PCE) of organic solar cells (OSCs). Herein, we report a molecular design strategy that harnesses luminescent-carbazole linkage site isomerism to suppress non-radiative recombination. Two carbazole-functionalized NFAs, QxCz‑C and QxCz‑N, were designed and synthesized. Theoretical calculations reveal that QxCz‑C adopts a coplanar conformation, whereas the carbazole unit in QxCz‑N is oriented nearly perpendicular to the main chain. Upon incorporating QxCz‑C as a minor guest into the host material BTP‑eC9, a favorable mixed phase is formed, accompanied by efficient energy transfer from the guest to the host. The photoluminescence quantum yield of the blend acceptor is significantly enhanced, effectively suppressing electron‑phonon coupling, thereby reducing non‑radiative recombination loss and improving Voc. Simultaneously, guest incorporation optimizes molecular packing order and active layer morphology, facilitating exciton dissociation and charge transport. Consequently, the PM6:BTP‑eC9:QxCz‑C device achieves a PCE of 20.53%. The generality of this strategy is further validated in the D18:L8‑BO system, delivering an excellent PCE of 21.10%. This work establishes a quantitative "connectivity topology-molecular conformation-non-radiative loss" structure-property relationship and provides a generalizable approach to overcoming the voltage bottleneck in OSCs.

Non-fused ring electron acceptors (NFREAs) exhibit substantial commercial application potential. Nevertheless, their subpar electron transport performance results in slightly low power conversion efficiencies (PCEs) of organic solar cells (OSCs). Herein, we put forward an innovative supramolecular side-chain-induced multi-dimensional charge transport strategy to exploit two NFREAs 3TT-Ph2 and 3TT-Ph4 with terminal phenyl/fluorinated phenyl side chains. In comparison to the unfunctionalized control molecule 3TT-2, both 3TT-Ph2 and 3TT-Ph4 form additional phenyl-acceptor (Ph-A) supramolecular interactions between the phenyl side groups and the cyanoindanone end groups. Meanwhile, these fluorinated terminal phenyl groups can induce the formation of multiple supramolecular interactions, including F···F, F···H and F···C. The synergistic effect of these supramolecular interactions promotes the tight and ordered stacking of molecules, facilitates the construction of multi-dimensional charge transport channel. Finally, D18:3TT-Ph4-based device achieved a record-breaking PCE of 19.12% and a fill factor of 80.65%. Our research pave aneffective strategy for the molecular design of high-performance NFREAs.

Efficient hole-transporting materials (HTMs) are crucial for improving the power conversion efficiency (PCE) and operational stability of perovskite solar cells (PSCs). Nevertheless, the rational design of organic HTMs that simultaneously combine suitable energy-level alignment, visible transparency, good chemical stability, facile film formation, and efficient hole-transport characteristics remains a major challenge. In this work, first-principles calculations were employed to investigate the structural, optical, electrochemical, solubility, chemical stability, and charge-transport properties of five spirofluorenedithiolane-based derivatives (SFT1-SFT5), designed through thiophene-bridged end-capped acceptor engineering of the parent SFT-STPA molecule. The designed HTMs exhibit suitable frontier orbital alignment with the perovskite absorber, indicating favorable hole extraction and transport. Their highest occupied molecular orbitals (HOMO) energies range from - 5.15 to -5.26eV, indicating improved stabilization relative to the reference molecule (-5.07eV). Moreover, the designed derivatives retain absorption maxima below 470nm, which helps minimize parasitic absorption and preserve effective light harvesting by the perovskite layer. Reduced reorganization energies (0.3032-0.3933eV), higher hole-transfer integrals (0.1250-0.1690eV), and rapid hole-transfer rates collectively indicate favorable hole-transport behavior. In addition, more favorable solvation free energies (-56.84 to -47.92kcal mol- 1) suggest improved processability and film-forming ability. Overall, these results identify spirofluorenedithiolane-based derivatives as promising HTM candidates for high-performance PSCs.

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.

Investigation of the conversion efficiency of series-connected CIGS solar cells irradiated with a multi-beam laser

Precise bandgap tuning is critical for maximizing the power conversion efficiencies (PCEs) of organic solar cells (OSCs). Here, we refined the Shockley-Queisser model by incorporating sub-bandgap absorption and nonradiative losses, predicting an optimal optical bandgap (Eg) of ∼1.41 eV for Y-series acceptor-based OSCs, higher than the ideal SQ value of 1.34 eV. Guided by this loss-aware target, we designed and synthesized a new acceptor (YCF3-BO) with CF3-terminated core- and branched outer-side chains to achieve the target Eg in PM6:YCF3-BO devices. The resulting binary and ternary devices achieved PCEs of 19.8% and 20.2%, respectively. This performance arises from two synergistic effects: tuning Eg into the refined optimum window enhances photoluminescence quantum yield and suppresses nonradiative recombination, while branched side chains promote a 3D charge-transport network. Furthermore, PM6:YCF3-BO-based photocathodes operated efficiently in underwater solar hydrogen production. This study establishes a unified framework integrating loss-aware bandgap theory with acceptor design and solid-state packing control for advancing organic photovoltaics.

Molecular engineering of porphyrin sensitizers is an effective strategy for improving the power conversion efficiency (PCE) of dye-sensitized solar cells (DSSCs). In this work, the synergistic effects of composite donor engineering and π-spacer modulation on the electronic structure, interfacial charge transfer, and photovoltaic performance of D-π-A porphyrin dyes were systematically investigated using DFT and TD-DFT calculations. Five sensitizers (L, T, T-L, TO-L, and T-LD) were designed by combining triphenylamine, indoline, methoxy modification, and acetylene π-bridges. The calculated results reveal that the composite donor strategy effectively improves energy-level alignment, promotes directional intramolecular charge transfer, and suppresses charge recombination. Among all sensitizers, the methoxy-modified dye TO-L exhibits the best overall photovoltaic performance, with the most favorable electron injection driving force (ΔGin = -2.24 eV), a low regeneration energy loss (ΔGre = 0.06 eV), efficient interfacial coupling, and a high theoretical PCE of 10.10%. Further analysis based on the dye-TiO2 interface demonstrates that conduction-band upshifts and interfacial dipole effects play critical roles in determining the balance between electron injection and open-circuit voltage. In contrast, the acetylene-bridged dye T-LD shows the largest absorption redshift and highest JSC owing to extended π-conjugation, but excessive electron delocalization weakens the actual injection driving force (ΔG0 = 0.28 eV) and increases reorganization energy, resulting in reduced VOC and PCE. These results reveal a clear spectral-voltage trade-off in highly conjugated porphyrin systems and demonstrate that synergistic optimization of donor strength, conduction-band alignment, and interfacial charge-transfer dynamics is more important than simply extending π-conjugation. This work provides valuable theoretical guidance for the rational design of high-efficiency porphyrin sensitizers.

Interface passivation is crucial to reduce nonradiative recombination losses at the perovskite-electron transport layer interface and enhance the power conversion efficiency (PCE) of perovskite solar cells. Various molecules are known to result in a gain in open-circuit voltage (VOC). However, this gain is often associated with increased instability. Here, we investigate the interface passivation of a Cs0.1FA0.6MA0.3Pb0.5Sn0.5I3 narrow-bandgap (1.26 eV) perovskite by ammonium iodide derivatives with multiple, primary, secondary, or tertiary ammonium iodide groups, connected via alkane linkers of different lengths to establish structure-property relationships. The impact of these passivators on interfacial recombination, charge extraction, and device stability is elucidated by tracking the quasi-Fermi level splitting (QFLS) of perovskite layers and perovskite/C60 bilayers, together with the VOC of complete solar cell devices over one month. All tested passivators reduce the nonradiative recombination losses at the perovskite/C60 interface, but the extent to which this translates into an improved photovoltaic performance strongly depends on the molecular structure. Short-chain primary diammonium passivators provide the most favorable balance between effective passivation and charge extraction, yielding QFLS values that closely match the device VOC. In contrast, extended and branched multiammonium passivators improve photovoltage stability but impede charge carrier extraction, leading to reduced fill factors (FF) and short-circuit current densities (JSC). Secondary ammonium terminal groups promote crystallite formation on the perovskite surface, which reduces the efficacy of passivation. Importantly, combining small with larger-sized passivators in a single layer enables simultaneous enhancement of QFLS, VOC, FF, and operational stability.

Surface passivation has played an essential role in the rapid advancement of power conversion efficiency (PCE) in perovskite solar cells (PSCs). However, conventional passivation strategies predominantly rely on small molecules such as ammonium-based ligands, which are prone to deprotonation under light exposure and thermal stress, leading to compromised device stability. Here, we report a polymerizable surface passivation material, vinylphosphonic acid (VPA). The vinyl group enables in situ polymerization, while the phosphate group passivates uncoordinated metallic defects. Both theoretical and experimental results confirmed that the polymerized-VPA (PVPA) forms a more robust and stable passivation layer than conventional organoammonium-based small molecules. Consequently, we achieved a PCE of 26.54% (certified as 26.24%). Benefiting from the more stable polymerized passivation layer, our devices demonstrate remarkable operational durability, retaining over 90% of their initial PCE after 1600 h at maximum power point operation under continuous 1-sun illumination. This approach provides a promising passivation layer strategy to enhance the stability and efficiency of perovskite solar cells.

The incorporation of non-hexagonal rings into nanographenes (NGs) would significantly alter their geometry and electronic structures, unlocking new application potential. However, the precise integration of consecutive pentagon-octagon into NGs remains synthetically challenging due to the associated high strain and the limitation in design strategy. Herein, we report an unprecedented horse-saddle non-benzenoid NG (HN1) embedding four pairs of pentagon-octagon units. The synthesis proceeds through two key steps: a tetramerization of 3-bromoacenaphthylen-1(2H)-one, followed by a three-fold Pd-catalyzed annulation with a diacetylene derivative. Single-crystal X-ray diffraction confirms that HN1 adopts a unique horse-saddle geometry induced by the four adjacent octagons. The fused pentagon-octagon pairs of NG impart configurational stability, high solubility, multiple reversible redox behavior, and a distinct antiaromatic character arising from the core structure. Notably, the incorporation of HN1 as an additive in the perovskite active layer significantly enhanced the power conversion efficiency (PCE) of perovskite solar cells from 20.60% to 22.61%. This work not only provides a synthetic approach to negatively curved NGs with contiguous nonhexagonal motifs but also explores their promising application in emerging optoelectronic devices.

Machine-learning-assisted optimization of power conversion efficiency in perovskite solar cells

Despite the impressive power conversion efficiency (PCE) of perovskite solar cells (PSCs), their long-term operational stability remains compromised by endogenous ion migration and interfacial recombination. Herein, we report a robust strategy by introducing a novel multifunctional cathode buffer layer based on 4,4'-((1,10-Phenanthroline-3,8-diyl)bis(ethyne-2,1-diyl))dianiline (BAE-Phen), which exhibits excellent thermal stability. Theoretical simulations and experimental characterizations reveal that BAE-Phen operates through synergistic mechanisms: its phenanthroline core strongly coordinates with metal ions to decelerate detrimental electrode corrosion, while its extended π-conjugated backbone enhances π-π stacking with the [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) electron transport layer, facilitating efficient charge transfer. Consequently, the optimized BAE-Phen-based devices achieve a champion PCE of 27.07% (certified 26.85%). Notably, unencapsulated devices retained 90.5% of their initial PCE after 2000h of thermal aging at 85°C. Furthermore, encapsulated devices maintain nearly 100% of their initial performance after 2200h of continuous maximum power point tracking under 1-sun illumination, demonstrating exceptional thermal and operational stability. This work presents a strategic interface engineering approach using a multifunctional molecular buffer, providing pivotal insights into the synergistic optimization of charge transmission and ionic to electronic stability for next-generation photovoltaics.

How to reduce energy loss by enhancing the photoluminescence quantum yield (PLQY) is currently one big bottleneck to further increase the open-circuit voltage (VOC) and power conversion efficiency (PCE) of organic solar cells (OSCs). Utilizing the aggregation-induced emission (AIE) effect should be effective to enhance the PLQY. However, there is no reliable molecular design strategy to realize AIE while maintaining the appropriate aggregation behavior of materials. In this study, through cleavage of the conjugated structure of the shamrock-shaped molecule of AQ-fNI, a nonfullerene acceptor (NFA), AQ-NI, with AIE effect was developed. AQ-NI exhibits a higher PLQY (14.6%) than that of AQ-fNI (6.16%), enabling an exceptionally low energy loss of 0.494 eV and consequently a high VOC of 0.960 V. Moreover, the becoming stacking characteristics of AQ-NI facilitate the modulation of aggregation behavior in the active layer, resulting in a favorable phase-separated morphology and enhanced charge carrier transport. As a result, the layer-by-layer (LBL)-fabricated binary OSCs based on D18/AQ-NI achieved a high PCE of 19.14%. In addition, AQ-NI could serve as a guest molecule in a bulk-heterojunction structure, and D18:L8-BO:AQ-NI-based ternary OSCs realized an improved PCE of 20.22% in comparison with the D18:L8-BO-based binary device (PCE = 19.39%). Our findings provide a simple and promising strategy for designing high-performance NFAs with AIE effect and establish a fundamental correlation between AIE properties and OSC performance.

Molecular structure modification of nonfullerene acceptors (NFAs) is an important approach to modulate optoelectronic properties and to improve power conversion efficiency of organic solar cells (OSCs). Herein, to deeply understand the influence of central-fused ring halogenation and extension on photoelectric properties and photovoltaic performances, we selected a series of NFAs with different central fused rings, including CH-6F, CH-20, CH-22, CH-23, CH-45, CH-BQ, CH-iBQ, and CH-BBQ, combined with electron donor PM6. Based on quantum chemical calculations, the geometric structures, electronic structures, excitation properties, and absorption spectra were systematically studied for the PM6 and NFA molecules, as well as the corresponding interface model complexes. Moreover, the rate constants of the electronic processes were discussed. The results indicate that the peripheral halogen substitution on the central fused ring can effectively enhance molecular backbone planarity, shrink dipole moment, lower the HOMO and LUMO energies with widening energy gap, induce blue shift of optical absorption, increase excitation energy and average electrostatic potential (ESP), and shorten excited-state lifetime. Extending conjugation of the central fused ring not only enhances molecular backbone planarity, lowers the HOMO and LUMO energies, and increases the average ESP and charge-transfer excitation energies but also reveals the importance of the fusing style for extending conjugation. This work unravels the trilateral relationship among molecular structures, properties, and photovoltaic performance of NFAs and provides foundations to design more efficient NFAs for OSCs.

At present, the power conversion efficiency of perovskite solar cells has exceeded 27%, attracting increasing attention from both academia and industry. However, fabricating high-efficiency devices typically requires inert atmospheres, which inevitably increase manufacturing costs and hinder large-scale commercialization of perovskite solar cells. This review systematically summarizes recent progress in the fabrication of perovskite solar cells under ambient air conditions. The effects of ambient environmental factors on perovskite precursor solutions and perovskite films are discussed in detail. Special attention is devoted to systematically analyzing different strategies, including buried-interface, bulk, and top-surface treatments for perovskite films, and their impact on the performance of perovskite solar cells fabricated in ambient air. Finally, the current challenges associated with ambient-air fabrication are summarized, along with a feasibility analysis and a perspective on future development.

This work focuses on how the structural regulation of nonfullerene acceptors (NFAs) improves the power conversion efficiency (PCE) of organic solar cells through terminal substitution and central core extension. Three series of NFAs (DONAD-X, DPT-X, and DOYAD-NO2) are designed by introducing different strong electron-withdrawing terminal substituents (X) and extended conjugated central cores (Y). High-precision density functional theory (DFT) and time-dependent DFT calculations are employed to comprehensively investigate their ground-state and excited-state properties. The calculation results reveal that strong electron-withdrawing terminal substituents are beneficial for NFA to effectively reduce the molecular energy gap, broaden the absorption spectrum, and increase the electron mobility. Symmetric substitution is more effective than asymmetric substitution in achieving longer maximum absorption wavelength and smaller excitation energy. The introduction of symmetric terminal substitution and synergistic effect of both -CN and -NO2 groups (abbr -CNO2) enables NFA to achieve optimal performance. Furthermore, the extended conjugated central cores effectively enhance the chemical reactivity and intramolecular charge transfer (ICT) of the NFAs. Based on the selection of the optimal terminal substituent and central core, we construct the most promising acceptor DOIAD-CNO2 and find that the PM6/DOIAD-CNO2 interface possesses the largest short-circuit current density and PCE (16.39%). The CT mechanisms of the designed PM6/NFA interfaces involve the coexistence of hot exciton excitation, intermolecular electric field, and direct excitation, which can promote more exciton separation. PM6/DOIAD-CNO2 has the most CT and FE/CT states with larger oscillator strengths, thereby obtaining the largest PCE. This work can inspire the experimental synthesis and application of these acceptor candidates and provide guidance for further design and development of more efficient NFAs.

ABSTRACT The limited charge carrier diffusion length of organic photovoltaic materials cannot afford separated charge carriers to efficiently diffuse to be collected at electrodes, which impedes the further enhancement of power conversion efficiencies of organic solar cells. Herein, a giant‐molecule electron acceptor with heavy atoms, viz. GMA‐Se‐Cl, is developed and incorporated into L8‐BO to prolong charge carrier diffusion length and improve power conversion efficiencies via taking advantage of giant molecules and heavy‐atom effects. Introducing GMA‐Se‐Cl endows L8‐BO:GMA‐Se‐Cl with a lower molecular diffusion coefficient, suppressed molecular thermal motion, and higher crystallinity, compared with the pristine L8‐BO. Such enables L8‐BO:GMA‐Se‐Cl to afford weaker electron‐phonon coupling, reduced Huang‐Rhys factor, and lower trap density, thus contributing to enhanced charge carrier mobilities and lifetime for the prolonged charge carrier diffusion length. It helps to inhibit charge carrier recombination and facilitate charge transport in devices. Therefore, D18:L8‐BO:GMA‐Se‐Cl based organic solar cells achieve a higher power conversion efficiency of 20.24%, compared with D18:L8‐BO based ones (18.50%). It indicates that introducing giant‐molecule acceptors with heavy atoms is an efficient strategy to restrain molecular thermal motion and electron‐phonon coupling for prolonged charge carrier diffusion length and thus boost power conversion efficiencies of organic solar cells.

Although power conversion efficiencies (PCEs) of organic solar cells (OSCs) have exceeded 20%, their fabrications have to rely on acid-doped anode interlayers (AILs), which brings serious corrosion problems. Undoubtedly, non-corrosive AILs are indispensable for the industrialization of OSCs, but they hardly exhibit comparable performances to acid AILs, such as the classic PEDOT:PSS. Herein, we designed and synthesized two pH-neutral conjugated polyelectrolytes (CPEs) with straight linear conformation as AILs for efficient and stable OSCs. Compared to the zigzag CPE, the linear IDT-F exhibits a dominant face-on orientation, which can form an intermolecular packing pathway that well coincides with the charge transport direction in OSCs. Consequently, the IDT-F-based AIL exhibits an exceptional hole-transporting capability, even suppressing that of PEDOT:PSS. By utilizing the IDT-F-based AIL, an unprecedented PCE of 20.06% was achieved in the binary OSC, along with a fill factor of 82.2%. This not only represents the best performance reported to date for OSCs using a non-corrosive AIL but also substantiates that a CPE-based AIL can provide photovoltaic efficiencies exceeding 20%. Importantly, the IDT-F-based AIL can address the corrosion issues in OSCs due to the excellent chemical inertness, boosting a high device stability, so as to pave the way for practicable OSCs.

There are few examples of the function-oriented synthesis of atomically precise metal nanoclusters (NCs) whose ligand composition and geometry readily translate into device-level performance. Here, we report the design and synthesis of the pancake-like [Au12Ag30(SPh3,5-(CF3)2)10Br20]6- (Au12Ag30) NC, and its use to boost the power conversion efficiency (PCE) and durability of perovskite solar cells. Single-crystal x-ray diffraction of Au12Ag30 revealed an Au12 icosahedron wrapped by a six-layer Ag30 shell, the (100) facets of which are capped by 20 Br- ligands, with 10 -CF3-bearing thiolates forming a hydrophobic equatorial belt. Introducing 0.5mg/mL of this cluster into ((FA0.95Cs0.05)PbI3)0.975(MAPbBr3)0.025 perovskite films boosted the device PCE from 23.55% to 25.53% and enables 94.8% retention after 1142h of continuous one-sun illumination. Au12Ag30 is also distinguished by its -6 superatomic charge, and 66.7% surface halogen coverage-the highest ever reported. These findings establish anisotropic halide/thiolate-protected NCs as potent additives for simultaneous defect passivation and environmental protection in high-efficiency optoelectronics.

The development of Y-series nonfullerene acceptors (NFAs) has significantly advanced the power conversion efficiency (PCE) of organic solar cells, surpassing 20%, while also demonstrating promising performance in bulk-heterojunction photocatalysis. Extending the π-conjugation of end groups is an effective strategy to tune molecular energy levels, enhance optical absorption, and optimize intermolecular packing, yet the effects on both photovoltaic and photocatalytic performance remains insufficiently explored. NFAs featuring an indanone-based central core have demonstrated excellent photovoltaic and photocatalytic performance. In this study, we design two novel NFAs, NQF-F and NQF-FN, derived from a common indanone-based NQF backbone, incorporating phenyl- and naphthyl-fuzed indanone end groups. The extended π-conjugation in NQF-FN results in broader absorption, improved charge transport, and a higher PCE of 17.06%, outperforming NQF-F (16.29%). More importantly, PM6:NQF-FN-based photocatalysts achieve a hydrogen evolution rate of 217.5 mmol h-1 g-1 with only 10 wt% Pt, compared to 214.4 mmol h-1 g-1 for PM6:NQF-F, despite a fourfold reduction in Pt content. These findings underscore the potential of end-group conjugation extension to enhance both photovoltaic and photocatalytic performance while reducing reliance on precious metals, providing critical design insights for multifunctional NFAs in energy conversion applications.