A single organic semiconductor typically struggles with inefficient intrinsic charge generation due to large binding energy (EB ≈ 0.5 electron volts) of Frenkel excitons, particularly in narrow-bandgap organic semiconductors that exhibit near-infrared (NIR) absorption. Here, we develop double-cable polymer–based nanoparticles (NPs), enabling single-component organic photocatalysts to achieve NIR photon absorption and generate long-lived free charges simultaneously. as-DCPIC, a double-cable polymer with donor polymer (PBDB-T) as electron-donating conjugated backbones and pendent NIR acceptor (TPDIC) as the electron-deficient side chains, offers potential for self-sustained photoelectric conversion. Consequently, as-DCPIC NPs exhibit significantly enhanced hydrogen evolution performance (11.88 mmol per hour per gram) compared to pristine PBDB-T or TPDIC NPs. Transient absorption spectroscopy elucidates the effective electron-hole separation inside as-DCPIC NPs, whereas decay kinetics monitor the long-lived free carriers (109 nanoseconds) in as-DCPIC NPs. Our findings demonstrate that double-cable polymers provide a powerful platform for establishing efficient single-component organic photocatalysts to generate long-lived reactive charges.

The effect of energy inhomogeneity in monomers forming a molecular aggregate is studied theoretically within the Frenkel exciton approach. It is shown that this inhomogeneity affects the optical characteristics, reducing the resonance light absorption and luminescence of a one-dimensional molecular aggregate. It is also shown that such an inhomogeneity enlarges the widths of frequency regions, in which such an absorption and luminescence take place. We show that the effect of monomer energy inhomogeneity drastically differs from the effect of inhomogeneity in exciton hopping.

Abstract An exciplex, a charge‐transfer state formed at a donor–acceptor (D–A) heterojunction, plays a crucial role in organic photonic devices. Although binding energy significantly influences the exciplex energy and is often decisive in the relative alignment to Frenkel exciton levels, its exact determination remains challenging due to the disordered arrangement of heterodimers in amorphous mixture, leading to heterogeneous energy broadening. In this study, the distribution of the binding energies in organic D–A mixtures is investigated, focusing on the impact of different acceptor molecules in different shapes. A model is introduced that incorporates molecular size and ionic charge localization as key parameters, which successfully reproduces the statistical results of the exciplex binding energies in amorphous mixtures using TD‐DFT calculations. Furthermore, the model predicts that large molecules with ionic charges confined to their edges exhibit low exciplex binding energies, whereas smaller molecules with delocalized ionic charges across their molecular planes result in higher binding energies, which is consistent with experimental observation. These findings provide valuable insights for designing exciplex hosts for photonic applications, particularly for blue OLEDs, which are critical for advancing display technology, where the energy budget for developing higher‐energy exciplexes than a deep blue emitter is rather limited.

Topological photonics offers a versatile platform for designing advanced photonic materials and devices, such as one-way waveguides, on-chip optical isolators, and topologically protected lasers. Recently, particular interest has emerged in exploring topologically protected polariton lasing. However, current topological polariton lasers mainly rely on inorganic semiconductors, suffering from cryogenic temperature operation and limited applicability due to the small binding energies of Wannier-Mott excitons. Here, we realize room-temperature topological polariton lasers by exploiting tightly bound Frenkel excitons in organic semiconductor lattices. The Frenkel excitons strongly couple with microcavity photons to generate stable exciton polaritons. By modulation of the intra- and intercell coupling strengths of organic semiconductor lattices, room-temperature polariton lasing is achieved at topological edge states. The topological polariton laser exhibits a temperature-controlled wavelength-tunable laser output. This work demonstrates organic semiconductors as promising material systems for topological polariton devices.

The interplay between coherence and system-environment interactions is at the basis of a wide range of phenomena, from quantum information processing to charge and energy transfer in molecular systems, biomolecules, and photochemical materials. In this work, we use a Frenkel exciton model with long-range interacting qubits coupled to a damped collective bosonic mode to investigate vibrationally assisted transfer processes in donor-acceptor systems featuring internal substructures analogous to light-harvesting complexes. We find that certain delocalized excitonic states maximize the transfer rate and that the entanglement is preserved during the dissipative transfer over a wide range of parameters. We investigate the reduction in transfer caused by static disorder, white noise, and finite temperature and study how transfer efficiency scales as a function of the number of dimerized monomers and the component number of each monomer, finding which excitonic states lead to optimal transfer. Finally, we provide a realistic experimental setting to realize this model in analog trapped-ion quantum simulators. Analog quantum simulation of systems comprising many and increasingly complex monomers could offer valuable insights into the design of light-harvesting materials, particularly in the nonperturbative intermediate parameter regime examined in this study, where classical simulation methods are resource intensive.

The photo-charge generationfrom localized Frenkel excitons (EXs) reduces the theoretical power conversion efficiency (PCE) of organic solar cells (OSCs) below Shockley-Queisser limit as extra energy is required for EX splitting at heterojunctions. Though developing the intrinsic photo-charge pathway based on intermolecular charge transfer (ICT) excitons is expected to break the efficiency bottleneck, its current contribution to charge photogeneration is negligible due to the difficulties in spontaneous ICT dissociation. To amplify the intrinsic photo-charge utilization, a concept of bulk homojunction (BHOJ) within non-fullerene acceptors (NFAs) is proposed. Under this structure, the EX converts to ICT in NFA grains, whereas the anisotropic molecular orientation at grain boundaries drives ICT splitting. To fulfill the morphological requirements, a co-solvent strategy is taken: a good main solvent, chloroform, guarantees the NFA's crystallinity, and a poor auxiliary solvent, acetone, helps the anisotropic grain formation. Taking advantage of the BHOJ, a fivefold growth of short-circuit current density (JSC) is observed in Y6-only OSCs. More importantly, its compatibility with cost-effective printing, fabrication, and semi-transparent devices is also confirmed in model devices, even with the existence of bulk heterojunction (BHJ) structure. This work highlights the BHOJ as a general morphological pursuit for future OSCs' improvements.

The interplay between Frenkel (FE) excitons and charge-transfer(CT) states crucially impacts exciton transport in organic molecularaggregates. Using large-scale nonadiabatic surface hopping dynamicson Holstein-type Hamiltonians parametrized for realistic systems,we here show that exciton diffusion strongly depends on the FE–CTenergy offset (ΔE) and the sign pattern ofexcitonic and electronic couplings. Hybridization at the bottom ofthe exciton band (H– and J+) promotesdelocalized states with moderate CT character (30–50%), boostingdiffusion coefficients by up to an order of magnitude. In contrast,hybridization at the top of the band (H+ and J–) leads to stronger localization and reduced transport. These trendspersist even under strong vibronic coupling, where band-based descriptionsfail, highlighting robust design principles for enhancing excitonmobility in organic materials.

Aggregation effects of molecular chromophores play a crucial role in determining the spectroscopic properties of solid‐state organic materials. Within this work, we focus on excitonic coupling and particularly the question of whether aggregation leads to H‐ or J‐type coupling, that is, whether the lowest energy excited state of the aggregate is optically bright or not. Employing a supermolecular picture to represent the different terms giving rise to exciton splitting, we develop an intuitive and generally applicable phenomenological model for estimating the sign and magnitude of the exciton coupling. This model, which is based on the shape of the monomer transition density is shown to be suitable across the whole range of relevant wave function types from purely Coulomb‐coupled Frenkel excitons to strongly charge‐transfer admixed excimer states. The implications are illustrated in the stacked anthracene and perylene‐diimide dimer systems. The presented model does not only explain the long‐range behavior but provides a clear explanation of atom‐scale oscillations in the couplings seen for these systems. We hope that this work will give a boost to modern molecular materials science by providing new insight into interactions in the solid state as well as by highlighting the power of going beyond a simple frontier orbital picture in the design of molecular materials.

Natural photosynthetic systems achieve remarkable energy transfer efficiency through the highly arranged network of integrated chromophores, where strong intermolecular excitonic interactions boost and direct the energy and electron migrations within the system. This article systematically explores how geometric arrangements of bacteriochlorophyll-like (BChl) dimers modulate excitonic couplings and spectral characteristics using a Frenkel exciton Hamiltonian (FEH) model coupled with multiconfigurational SA-RASSCF/MS-RASPT2 monomeric wave functions. Through extensive analysis of over 11,000 BChl dimeric configurations, we demonstrate how intermolecular distances, translation, and rotations around different axes drive transitions between H-, J-, X-, and (+)-aggregate types, with their distinct spectral and energetics landscape. Our results reveal significant deviations from classical dipole-dipole approximations in closely stacked dimers, highlighting the necessity of employing the FEH framework to describe Coulomb interaction between spatially extended transition densities. Rotational symmetry-breaking (e.g., pitch and yaw rotations) is shown to amplify or diminish coupling strength, with some spatial dispositions that mimic natural light-harvesting 2 design. Additionally, macrocycle curvature in BChl monomers imposes excitonic band asymmetry, thus introducing another path to fine-tune the system's properties. The comprehensive dataset outlines fundamental concepts and design principles for efficient artificial light harvesting and advanced exciton-based materials, offering potential for organic optoelectronic applications.

Metal-free polymeric semiconductors exhibit substantial potential in attaining photocatalytic solar energy conversion via exciton-based energy transfer, whereas their inefficient triplet-exciton yields caused by faint spin-orbit coupling set limits to the relevant applications. Here, we present an alternative pathway for harvesting long-lived triplet excitons in polymeric photocatalysts, where a charge-transfer exciton (CTE), rather than an intrinsic Frenkel exciton, hosted in donor-acceptor motifs is employed for triggering energy-transfer-mediated photocatalysis. By taking polymeric carbon nitride (PCN) as a prototype, we used an aromatic heterocyclic compound, 2,3-diaminopyridine (DAP), to modify the relevant excitonic properties. Spectroscopic and theoretical analyses confirm that DAP bonding brings about a subtle difference in electronic density distributions between adjacent tri-s-triazine units. Such a difference enables the formation of donor-acceptor motifs for accommodating a long-lived triplet CTE, without introducing additional undesired exciton-dissociation driving forces. Triplet CTE harvesting in DAP-modified PCN enables high-efficiency energy-transfer-mediated molecular oxygen activation for triggering selective naphthalene-derivative oxidation.

We report on the observation of an excited 2s state of a trion in a 4.2nm wide doped GaAs/Al_{0.3}Ga_{0.7}As quantum well using magneto-optical Kerr effect (MOKE) spectroscopy under out-of-plane magnetic fields up to 6T. This resonance appears slightly below the 2s exciton in energy. Strikingly, the 2s trion is found to be bound only for magnetic fields larger than 1T. The signature of the 2s trion is absent in the magnetoreflectance spectra, while it is detectable in the MOKE spectra signifying the importance of the powerful technique. Similar to the 1s states, the 2s trion shows an opposite degree of magnetic-field-induced polarization compared to its exciton counterpart, in agreement with our theoretical calculations. This transfer of oscillator strength between the complexes establishes an optical fingerprint of the 2s excited trion.

We use femtosecond pump-probe spectroscopy to study the coherent interaction of excited exciton states in WSe_{2} and MoSe_{2} monolayers via the optical Stark effect. For cocircularly polarized pump and probe, we measure a blueshift that points to a repulsive interaction between the 2s and 1s exciton states. The determined 2s-1s interaction strength is on par with that of the 1s-1s in agreement with the semiconductor Bloch equations. Furthermore, we demonstrate the existence of a 2s-1s biexciton bound state in the cross-circular configuration in both materials and determine their binding energy.

Two-dimensional organic single crystals (2D OSCs) offer high crystallinity and quantum limit properties, making them ideal for exploring unique quantum phases and developing scaled optoelectronic devices. However, accurately probing the structure-optoelectronic relationship in 2D OSCs remains challenging. Here we realize in situ optoelectronic characterization of 2D OSCs through an atomically precise thinning technique. Thinning 3D pentacene crystals to the monolayer limit induces a phase transition from Frenkel excitons to charge-transfer (CT) excitons, achieving a near-unity quantum yield (∼95.1%). In-situ electrical measurements demonstrate that this thinning improves carrier mobility and reduces threshold voltages. Utilizing 2D pentacene crystals, we construct a high-performance synapse device, showing a record paired-pulse facilitation index (PPF index ∼ 261%). This remarkable synaptic plasticity further allows us to emulate the human vision system, predicting the object trajectory with exceptional accuracy (∼99.1%). These results provide new insights into the intrinsic properties of 2D OSCs and lay the foundation for multifunctional optoelectronic applications.

A tunable plasmonic platform that allows room‐temperature hybridization of dissimilar excitons, namely of Wannier–Mott excitons in monolayer (1L) WS2 and Frenkel excitons in molecular J‐aggregates via simultaneous strong coupling (SC) to surface plasmon polaritons, is presented. It is based on a simple layered design consisting of a thin planar silver film and a dielectric spacer on which monolayer and the aggregates are assembled. SC is revealed by angle‐dependent spectroscopic ellipsometry measurements in total internal reflection geometry by the observation of double Rabi splitting at the two excitonic resonances. The exciton‐exciton‐plasmon system is analyzed with the coupled oscillator model, and modulation of polariton character and dynamics by the number of molecules participating in the coupling is demonstrated. Furthermore, a route is proposed to remotely control the mode splitting at the Frenkel excitonic resonance via electrostatic gating of the 1L‐WS2 and to switch the molecule–plasmon interaction between the weak and SC regime.

In quantum mechanics (QM) the theory of quantum transitions works only in atomic physics and in the adiabatic approximation (AA) in molecular and chemical physics. To restore the functionality of QM in molecular and chemical physics beyond AA, Egorov is forced to introduce the so-called dozy chaos (DC) into QM. DC is introduced by replacing the infinitesimal imaginary additive in the energy denominator of the total Green’s function of the system with a finite value. As a result, the transition between quantum states taken in AA becomes continuous, and QM itself becomes quantum‒classical mechanics (QCM). In the case of strong DC, QCM leads to the same results as QM. In the case of weak DC, a regular component in the transient state dynamics appears against the background of chaos. The coherent interaction of the regular component in the electron charge motion and the regular component in the reorganization motion of the nuclei in the environment leads to the so-called Egorov resonance (ER). The same chaos can be strong for small molecules (standard optical spectroscopy) and weak for large molecules (photochemistry and nanophotonics). Therefore, ER is also called nano-resonance. ER explains the nature of the well-known narrow and intense optical J-band of J-aggregates of polymethine dyes, discovered by Jelley and Scheibe in 1936. The first explanation of the nature of the J-band was given by Franck and Teller in 1938 based on the Frenkel exciton concept. This article discusses in detail the evolution of theoretical ideas about the nature of the J-band over almost a century of history and provides a deeply reasoned criticism of them. On the basis of QCM it is explained a large number of experimental data on the shape of optical bands in polymethine dyes and their aggregates. The nature of the physical source of life, possible alternative life forms and the idea of living materials are discussed.

Understanding how passivating surface ligands couple to excitonic states in nanocrystal photocatalysts is crucial for controlling nonradiative relaxation pathways which compete with interfacial charge transfer. Here, we report femtosecond transient infrared (IR) spectroscopy to resolve ∼100 fs ligand-exciton coupling between 1S exciton states in oleate-capped cadmium sulfide (CdS) nanocrystals and vibrational modes of surface carboxylates. Differential mid-IR spectra show distinct negative amplitude and positive photoinduced absorption signals at ∼1540 cm-1 (carboxylate asymmetric stretch) and ∼1440 cm-1 (carboxylate symmetric stretch), respectively. Fluence-dependent transient IR measurements reveal that the symmetric stretch is uniquely sensitive to picosecond Auger recombination, while the asymmetric stretch shows no analogous decay. Our results provide direct measurement of femtosecond ligand-exciton coupling in CdS nanocrystals and demonstrate how surface-bound carboxylate ligands serve as carrier-specific reporters of nanocrystal photophysics. These findings offer critical insights for designing and developing predictive models for ligand-mediated strategies in next-generation nanocrystal photocatalysts.

Near‐infrared (NIR) dyes can overcome the weak absorption of lanthanide nanoparticles (NPs) by antenna sensitization, offering new avenues to develop efficient and versatile lanthanide nanomaterials. However, current research on dye‐sensitized lanthanide NPs for photothermal conversion is still preliminary, and the involved excited‐state dynamics and interfacial interactions remain elusive. Herein, steady‐state/transient absorption spectroscopy and theoretical calculation are used to investigate the coordination and aggregation states of cypate dyes on NaNdF4 NPs, revealing the influence of interfacial interactions on resonant energy transfer. Synergetic heat‐generation mechanism of lanthanide cross‐relaxation and dye intermolecular collisions is further proposed. The photothermal conversion efficiency of cypate‐NaNdF4 nanocomposites reaches 50.4%, outperforming those of typical photothermal materials with high NIR absorption. Moreover, the intersystem crossing of cypate can be inhibited due to the depopulation of the S1 exciton via ET, thereby improving anti‐photobleaching ability. These dye‐sensitized NaNdF4 nanocomposites exhibit superior photothermal effect, stability and NIR‐II luminescence, showing great potential in theranostic applications.

Quantum confinement and reduced dielectric screeninglead to strongexcitonic effects in atomically thin transition metal dichalcogenides(TMDs). Encapsulation of TMD monolayers in hexagonal boron nitride(hBN) unveils the excitonic Rydberg series below the free particlebandgap. The nonequilibrium response and the dynamics of these higherorder exciton states and their multiparticle complexes remain almostunexplored. Here we use ultrafast pump–probe optical microscopyto measure the dynamics of excited-state (2s) excitons in hBN-encapsulatedmonolayer WSe2. 2s excitons form through an ultrafast relaxationprocess from high-energy states and exhibit longer decay dynamicsthan ground state excitons due to their higher spatial extension.We detect light-induced formation of 2s trions with significant oscillatorstrength and faster decay dynamics than 2s excitons, attributed toan intra-excitonic Auger effect causing an additional decay channel.Our results shed light on the dynamics of excited state excitons inTMDs and their interactions with free carriers.

The energy of sunlight is predominantly concentrated in near-infrared (NIR) region, posing a paramount limitation for practical application of conventional photocatalysts. Organic semiconductors can offer NIR absorption and tunable energy levels simultaneously through molecular engineering, which presents great potential in solar-driven catalysis. However, an individual organic semiconductor typically generates Frenkel excitons with large binding energy, hindering efficient electron-hole separation. Herein, we develop molecular-level heterojunction to suppress electron-hole recombination, thereby achieving a boosted hydrogen (H2) evolution reaction rate of 25.54µmol h-1 (12.77mmol h-1 g-1) under visible-near-infrared (Vis-NIR) light. Surprisingly, heterojunction nanoparticles (NPs) comprising donor polymer PBDB-T matched with an A-D1-D2-D1-A type acceptor BTPT-IC4F exhibit a promising external quantum efficiency of 6.3% at 730nm. Transient absorption spectroscopy monitors effective extraction of photogenerated holes from the highest occupied molecular orbital (HOMO) of BTPT-IC4F to the HOMO of PBDB-T, while first-principle calculations confirm the prolonged lifetime of excited BTPT-IC4F due to efficient hole capture by the PBDB-T phase. The outstanding performance of heterojunction NPs under NIR light is ascribed to strong hole transfer within the nanoparticle. This study provides valuable insights for designing molecular-level organic heterojunction photocatalysts toward NIR light-driven H2 evolution and other potential reactions.

An exciton–polariton condensate is a state of matter with collective coherence leading to many fascinating macroscopic quantum effects. Recently, optical bound states in the continuum (BICs) have been demonstrated as peculiar topological states capable of imparting novel characteristics onto the polariton condensates. Organic semiconductors featuring robust Frenkel excitons and high physicochemical tunability potentially offer a promising platform to explore topologically engineering of BIC polariton condensates at room temperature. However, a universal physical mechanism for engineering organic BIC systems has remained elusive, hindering the demonstration of BIC polariton condensates with topologically tunable macroscopic quantum effects. Here we report topologically reconfigurable room-temperature polariton condensates by systematically engineering the BICs in organic semiconductor metasurfaces. Two-dimensional organic metasurfaces are designed to support two polariton BICs with different topological charges. The organic Frenkel excitons with large binding energies allow for non-equilibrium polariton condensation at BICs at room-temperature. By virtue of the excellent physicochemical tunability of organic materials, we further explore the dynamic topological engineering of polariton lasers by manipulating the BICs in situ. Our results fundamentally promote the innovative design and topological engineering of polaritonic materials and devices.