Pressure was used to modulate interactions in an electron donor-acceptor system, composed of a zinc porphyrin (ZnP) and a fullerene (C60), held together by an amidinium-carboxylate salt-bridge (ZnP-H⋯C60). Two different trends evolved in steady-state absorption assays. Volume compression causes an absorbance intensification, and a solvatochromic-like red shift that stems from increased E-field density. Pressure-dependent femtosecond and nanosecond transient-absorption experiments were performed to investigate the activation volumes of the excited-state deactivation processes in ZnP-H⋯C60. Solvent relaxation of S1 is found to have a highly positive ΔV k2 ‡. The pressure-induced rate attenuation for this process is assumed to be linked to the solvent's viscosity increase. Intersystem crossing to the porphyrin-centered T1 state is free of intrinsic and extrinsic reorganizations and, as such, the activation volume is close to zero. The same applies for the subsequent ground-state deactivation from T1 to S0. Charge-separation to afford (ZnP)˙+⋯H⋯(C60)˙- is linked to a volume compression towards the activated state with ΔV k3 ‡ = -5.7 ± 2.2 cm3 mol-1. The charge-recombination undergoes, within the experimental margins of error, an equal volume expansion with ΔV k4 ‡ = +8.6 ± 0.7 cm3 mol-1. This effect is linked to the generation and/or neutralization of charges, best described by the Jung equation for electrostrictive volume changes in dipolar zwitterionic entities. Importantly, volumetric contributions from a possible PT towards the activated state were not observed.

ZUSAMMENFASSUNG Eine robuste externe Steuerung der Spinkommunikation in molekularen Gerüsten ist für potenzielle Anwendungen in der Quanteninformationswissenschaft sehr erstrebenswert. In dieser Arbeit integrieren wir zwei Arten von Dithienylethen‐Einheiten (DTE) in Tris(2,4,6‐trichlorophenyl)‐methyl (TTM) basierte Diradikaloide und berichten über das erfolgreiche bistabile Schalten der optischen und magnetischen Eigenschaften des Moleküls. Die Bestrahlung der offenen Form mit sichtbarem Licht erzeugt bis zu 97 % die geschlossene Form, in der die Konjugation der zwei Radikalzentren zu einer Absorption über den gesamten sichtbaren Spektralbereich sowie zu einer Verdopplung der Singulett‐Triplett‐Energielücke führt. Diese Ergebnisse etablieren TTM/DTE‐Hybride als persistente und auf mehreren Ebenen schaltbare Diradikaloide.

Precise control over thin-film morphology and interfacial organization is essential for solution-processed organic electronics. We demonstrate the successful Langmuir-Blodgett (LB) fabrication of nanometer-precise, uniform PM6 and N2200 polymer films. Optimized solvent and spreading conditions yield controlled assembly of uniform and homogeneous mono- and multilayers. PM6 formed isotropic films with tangled coiled structures, while N2200 showed anisotropic domains with directional π-stacking and extended branch-like polymer chains. Nanomechanical analysis revealed a 35-40% increase in surface elasticity for multilayers versus monolayers. Surface potential measurements underlined a thickness-dependent transition from substrate-dominated electrostatics in monolayers to a bulk-like behavior in multilayers, while photoluminescence mapping confirms preservation of emissive functionality even down to a monolayer. Preliminary photoresponsivity tests with photoactive layers below 20 nm show a reproducible increase in short-circuit current density upon increasing the number of PM6 and N2200 layers from five to six each, as confirmed by measurements across multiple devices. This trend is attributed to an absorption cross section that scales with increasing layer thickness. Our results position the LB method as a robust platform for constructing ultrathin, structurally coherent, and electronically active polymer interfaces with nanometer-scale thickness control.

The inherent susceptibility of n-type organic semiconductors to molecular dioxygen (O2) results in electron trapping or in unintended p-doping, which in turn diminishes their electron mobility. This concept is challenged in the present study by exploring O2 interactions with organic charge-transfer complexes (CTCs), where electron donor-acceptor interactions generate partially delocalized electronic states. Using a CTC comprising a phenazine electron donor and a 7,7,8,8-tetracyanoquinodimethane (TCNQ) electron acceptor, we demonstrate that its exposure to O2 does not lead to electron extraction but instead enhances the charge-transfer activity. The increased electron density at the TCNQ acceptor upon CTC exposure to O2 is attributed to electron trap-states passivation by O2, without evidence of chemisorption. This passivation mitigates recombination losses, resulting in a threefold photoluminescence quantum yield increase, enhanced electrical conductivity, and improved charge-transfer state efficiency. Similar O2-mediated conductivity enhancements are observed across additional donor-acceptor pairs, proving the broader applicability of this effect, and paving the way for designing O2-enhanced advanced organic electronic materials.

Diketopyrrolopyrrole (DPP)-based terpolymers have emerged as promising donor materials for organic solar cells (OSCs), offering tunable optoelectronic properties, broadband absorption, and enhanced morphological stability through random terpolymerization strategies. This study investigates the ultrafast charge carrier dynamics of three DPP-based terpolymers, (P1-P3), incorporating different ratios of fluorobenzotriazole (FTAZ) and thienothiophene-capped DPP (TTDPP) acceptors. Using femtosecond transient absorption spectroscopy, we examine how acceptor ratios and thermal annealing influence photophysical processes in pristine terpolymers and their bulk heterojunction blends with PC71BM. Increasing the TTDPP content enhances backbone planarity, π-π stacking, and charge delocalization, thereby reducing recombination losses and promoting efficient charge separation. Compared to P2 and P3, the P1 terpolymer, with the highest TTDPP ratio, exhibits the most favorable intramolecular charge transfer kinetics and balanced carrier mobilities, consistent with its superior photovoltaic performance. Thermal annealing, however, reduces long-lived charge populations in all blends due to fullerene aggregation, which diminishes phase separation. These findings highlight how rational tuning of acceptor ratios in DPP-based terpolymers provides a pathway toward optimizing both efficiency and stability in OSCs.

The preparation of gradients of active layers in organic solar cells reveal a remarkable alignment effect at the interface of oxide and organic material induced by a small molecule.

Robust external manipulation of spin communication in molecular frameworks is desirable for potential applications in quantum information science. Herein, we incorporate two types of dithienylethene (DTE) units into tris(2,4,6-trichlorophenyl)methyl (TTM)-based diradicaloids and report on the successful bistable switching of the optical and magnetic properties of the molecule. Visible-light irradiation of the open form generates up to 97% of the closed form, in which conjugation between the two radical centers leads to absorption over the entire visible range of the spectrum as well as a twofold increase of the singlet-triplet gap. These results establish TTM/DTE hybrids as persistent and multi-level responsive diradicaloids.

Supramolecular host-guest systems possess fascinating properties arising from the confinement and relative motions of molecules in cavities, which are often difficult to characterize and understand, particularly as molecular complexity increases. Due to their hierarchical and relatively rigid multi-level structure, supramolecular Matryoshka architectures are exceptionally well-suited to develop and test experimental and computational methods on supramolecular dynamics. Here, we combine atomistic molecular dynamics, metadynamics simulations, and femtosecond/nanosecond transient absorption spectroscopy to characterize two fullerene⊂[n]CPP⊂nanocage assemblies, C60⊂[10]CPP⊂6·(BArF)8 and C70⊂[11]CPP⊂6·(BArF)8. The results that we obtain allow us to understand in detail the internal dynamical degrees of freedom of the molecular subparts composing the supramolecular matryoshkas, discerning and characterizing fluctuations, unbinding, and relative rotation of the encapsulated guests. Femto- and nanosecond transient absorption spectroscopy studies corroborate an effective intermolecular electron transfer between the nanocapsule and C60 in the C60⊂6·(BArF)8 and C60⊂[10]CPP⊂6·(BArF)8 assemblies after photoexcitation, which is consistent with the concerted and reciprocal motions of the subcomponents that are observed in the simulations.

Abstract Fused filament fabrication (FFF) 3D printing provides an accessible route to fabricating retrievable photocatalytic architectures with tunable geometry and composition. Here, we address the limited recoverability and reusability of conventional powder-based photocatalysts by translating a metal-free semiconductor catalyst to 3D printed electrodes. Graphitic carbon nitride (g-C3N4) was functionalized with carbonized polydopamine (cPDA) to create a modified photocatalyst with improved photophysical behavior, consistent, more effective charge separation, and longer-lived photoexcited states, which correlates with enhanced photocatalytic activity. The optimized formulation was compounded into an extrudable PLA-based composite filament and printed into electrodes containing either g-C3N4 or g-C3N4/cPDA. The printed g-C3N4/cPDA electrodes show enhanced photocatalytic rhodamine B degradation under simulated sunlight compared with unmodified printed electrodes. In contrast to suspended powders, the electrodes enable straightforward retrieval, improved operational stability, and reuse without postseparation steps. Furthermore, we demonstrate that electrode performance can be increased by scaling the surface area, highlighting geometry as a simple handle for upscaling. This work demonstrates the potential of photocatalytic 3D printed electrodes made from abundant materials via low-energy processing as a scalable and sustainable route for wastewater treatment.

Understanding how molecular structure governs photoinduced spin evolution in organic diradicals is essential for the rational design of spin-responsive molecular materials. Here, we investigate temperature-dependent excited-state relaxation dynamics of syn- and anti-indenoindenodibenzothiophene (IIDBT) diradicaloids using variable-temperature steady-state and transient absorption spectroscopies. Vibronic progressions in the high-energy, nonfrontier-orbital π-π* transition absorptions and low-energy frontier-orbital transition absorptions prompt strong couplings between electronic excitation, on one hand, and molecular vibrations, on the other hand. With the help of ultrafast spectroscopy, we identified multistep excited-state relaxation pathways including a "hot" singlet excited state, an intermediate state of mixed electronic and spin character, and a long-lived triplet excited state, following either low- or high-energy excitations. Notably, intersystem crossing (ISC) in IIDBT diradicaloids is enabled by vibrationally activated spin-orbit coupling, in which spin-vibronic coupling enhances singlet-triplet mixing along nuclear coordinates, leading to a fast and efficient interconversion between singlet and triplet excited states. Molecular control over both the vibronic coupling strength and spin evolution is also emphasized. This work establishes a clear experimental link between molecular vibration and spin-dependent excited-state dynamics in organic diradicals, providing a general framework for understanding and controlling ISC in open-shell organic systems.

We describe herein the preparation of exfoliated transition-metal dichalcogenides (TMDs) and their heterostructures with phthalocyanines complemented by their in-depth (photo)physical investigation. We focused on six different zinc phthalocyanines (ZnPcs) as light harvesters and electron donors/acceptors. All of them were shown to interact strongly with the exposed surface of TMDs in dispersion (s-TMD) as well as thin film nanosheet networks (NN-(s-TMD)). The corresponding heterostructures, that is, ZnPc@NN-(s-MoS2) and ZnPc@NN-(s-WS2), were characterized by steady-state and pump-probe femtosecond transient absorption spectroscopy, as well as Raman and X-ray photoelectron spectroscopies (XPS) to shed light onto electron donor-acceptor interactions. Supported by density functional theory calculations and molecular dynamics simulations, we identified newly evolving charge-transfer absorptions in the electronic ground-state and confirmed the separation of charges in the electronic excited-state. Importantly, the direction in which charges flow in the electronic excited state depends on the relative positioning of the TMD bands and the molecular orbitals of the different ZnPcs. Key to control is tailoring the energetic position of the ZnPc HOMOs and LUMOs relative to the TMD bands.

ZUSAMMENFASSUNG Die intrinsische Empfindlichkeit von organischen n‐Halbleitern gegenüber molekularem Sauerstoff (O 2 ) führt zu Elektroneneinfang oder zu unbeabsichtigter p‐Dotierung, welches wiederum die Elektronenmobilität verringert. Dieser Grundsatz wird mit der vorliegenden Studie herausgefordert, in der die Wechselwirkung von O 2 mit organischen Ladungstransferkomplexen (CTCs) untersucht wird, bei denen Elektronendonor‐Akzeptor‐Wechselwirkungen teilweise delokalisierte elektronische Zustände erzeugen. Am Beispiel eines CTCs aus Phenazin als Elektronendonor und TCNQ als Elektronenakzeptor wird aufgezeigt, dass die Zugabe von O 2 nicht zum Elektroneneinfang führt , sondern stattdessen die Ladungstransferaktivität verstärkt. Die erhöhte Elektronendichte am TCNQ‐Akzeptor bei Exposition des CTC mit O 2 wird auf die Passivierung der für den Elektroneneinfang verantwortlichen Defekte durch O 2 zurückgeführt, ohne dass Anzeichen für eine chemisorptive Wechselwirkung vorliegen. Diese Passivierung mindert Rekombinationsverluste, was zur Verdreifachung der Photolumineszenz‐Quantenausbeute, einer erhöhten elektrischen Leitfähigkeit und einer verbesserten Effizienz des Ladungstransferzustandes führt. Ähnliche O 2 ‐vermittelte Leitfähigkeitssteigerungen werden auch bei weiteren Donor‐Akzeptor‐Paaren beobachtet, was die breitere Anwendbarkeit dieses Effekts belegt und den Weg ebnet zur Entwicklung von verbesserten Materialien im Bereich organische Elektronik, deren Leistungsparameter durch O 2 erhöht werden.

We report on the synthesis of a hydrogen‐bond mediated bola‐type supra‐amphiphile and assembly thereof in water. The assembly is based on amphiphilic porphyrins and hydrophobic perylenebisimdes (PBI), which both form the resulting bola‐form solely through the H‐bonding motif, which is shielded by the assembly of the chromophores itself. The amphiphilic porphyrin was functionalized, on one hand, with a cyanuric acid and, on the other hand, with an oligo carboxylate dendron as polar head group. Two Hamilton receptors were linked to the PBI on each imide position. Assembly was achieved by lyophilizing solutions of both components in water/THF mixtures, followed by redispersion in pure water yielding stable suspensions. Cryogenic transmission electron microscopy (cryo‐TEM) and dynamic light scattering (DLS) reveal a spherical morphology with diameters ranging from 15 – 100 nm. Once formed, the assemblies showed broadened absorptions and quenched PBI‐centered fluorescence. Using time‐resolved absorption spectroscopy, the nature of the fluorescence quenching was confirmed to be either charge separation, by which the porphyrin donates an electron to the PBI, or symmetry breaking charge separation, by which π‐π stacked PBIs donate and accept electrons. Denaturation of the supra‐amphiphile went hand‐in‐hand with a reinstation of the PBI fluorescence and suppression of charge separation.

In this study, we investigated the mechanistic factors that govern the selective photocatalytic reduction of CO2 over protons within a simple π-conjugated N-heterocycle, proflavine. Diluted conditions, where aggregates of 65 nm are formed, favored the selective CO2 photo-reduction, while the gradual transition to concentrated conditions enabled photo-reductive H2 generation. Proton reduction is coupled to larger aggregates, in which an alternative photo-relaxation pathway is active. We used transient absorption spectroscopy to corroborate that at low proflavine concentrations the presence of an electron donor triggers the one-electron reduced proflavine to perform the direct CO2 reduction. At high proflavine concentrations, protonation of the one-electron reduced proflavine was favored due to a positive shift in basicity in larger aggregates with sizes over 1 µm. In turn, H2 abstraction began with a pair of one-electron reduced, protonated, intermediates. Our study demonstrates an effective approach to limiting water reduction, a key challenge in advanced metal-free organic photocatalysis.

A polyfluorinated pentacene dimer, linked with a 1,3-diethynylphenylene spacer, was synthesized to investigate the effects of fluorination on the dynamics of singlet fission (SF). The incorporation of bulky 4,6-substituents on the phenylene spacer was necessary to improve the solubility of the fluorinated dimers, toward easier purification and analysis. Photophysical characterization shows that the incorporation of fluorine at the peripheral positions of the pentacene moieties inhibits the solvent dependence of the excited state observed in a nonfluorinated pentacene reference compound. Computational analysis suggests that fluorination drives efficient intramolecular pi-stacking, limiting conformational flexibility. The results confirm that the reduction of polarizability and rotational freedom of the pentacene groups, imposed by fluorination, eliminates the influence of solvent polarity on singlet fission kinetics. The kinetic stability of the fluorinated and nonfluorinated dimers toward photosensitized endoperoxidation with O2 is also assessed and shows that SF contributes to the stability of nonfluorinated pentacenes, but not necessarily to the stability of their fluorinated counterparts.

Presented is a straightforward synthetic methodology toward a porphyrin-based "N-doped" nanographene that includes a chiral element. This central element is a "defective" hexa-peri-hexabenzocoronene (HBC) resembling pi-extended [5]-helicene, which is fused to two porphyrins via five rings in a beta-meso fashion. The conjugate shows excellent processability and exhibits fascinating photophysical characteristics, which were probed using optical spectroscopy and density functional theory calculations.

Two-dimensional (2D) materials are promising candidates for solar-driven desalination. However, conventional photothermal 2D materials like transition metal carbides and nitrides (MXenes) as well as transition metal dichalcogenides (TMDs) suffer from major limitations such as their complex synthesis and low photothermal conversion efficiency. In contrast, metal phosphorus trichalcogenides (MPCh3) do not display the same drawbacks and possess widely tunable bandgaps (1.2-3.5 eV), making them ideal candidates for solar desalination. Moreover, their properties and applications related to light-matter interactions can be further enhanced by coupling with other low-dimensional nanostructures, tailoring hybrid van der Waals heterostructures of mixed dimensionality. Herein, we report the synthesis of FePS3 nanosheets/carbon nanodots (CNDs) 2D/0D nanoheterojunctions and their photothermal response when integrated into a 3D photothermal evaporator. These nanoheterojunctions exhibited high photothermal conversion performance, with an average absorbance of 90.6% from the UV to the NIR and a temperature increase of 42 °C over the blank control under 1 sun illumination for 300 s. A high water evaporation rate of 1.68 kg m-2 h-1 was observed under the same condition. Photothermal conversion and water evaporation experiments, along with femtosecond transient absorption spectroscopy (fs-TAS), photoluminescence (PL) analysis, and finite-difference time-domain (FDTD) simulations, revealed that the incorporation of CNDs and formation of the nanoheterojunction synergistically enhance localized heating and light absorption, improve trapping efficiency, and optimize nonradiative transition pathways. This study demonstrates the disruptive potential of the rational design of high-performance 2D material hybrids through MPCh3-based nanoheterojunction engineering, unveiling its transformative capability for use in solar desalination and photothermal technologies.

Triplet dynamics in singlet fission depend strongly on the strength of the electronic coupling. Covalent systems in solution offer precise control over such couplings. Nonetheless, efficient free triplet generation remains elusive in most systems, as the intermediate triplet pair 1 (T 1 T 1 ) is prone to triplet-triplet annihilation due to its spatial confinement. In the solid state, entropically driven triplet diffusion assists in the spatial separation of triplets, resulting in higher yields of free triplets. Control over electronic coupling in the solid state is, however, challenging given its sensitivity to molecular packing. We have thus developed a hexameric system (HexPnc) to enable solid-state-like triplet diffusion at the molecular scale. This system is realized by covalently tethering three pentacene dimers to a central subphthalocyanine scaffold. Transient absorption spectroscopy, complemented by theoretical structural optimizations and steady-state spectroscopy, reveals that triplet diffusion is indeed facilitated due to intramolecular cluster formation. The yield of free triplets in HexPnc is increased by a factor of up to 14 compared to the corresponding dimeric reference (DiPnc). Thus, HexPncestablishes crucial design aspects for achieving efficient triplet dissociation in strongly coupled systems by providing avenues for diffusive separation of 1 (T 1 T 1 ), while, concomitantly, retaining strong interchromophore coupling without compromising rapid formation of 1 (T 1 T 1 ).