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Luminescent radicals are attracting attention as emitters in electroluminescent devices thanks to the exploitation of doublet excitons. Recent studies reveal that exciton formation in radical organic light‐emitting diodes (OLEDs) primarily occurs through a charge trapping mechanism. Although typically detrimental for OLEDs, this might be a key process to elucidate light emission in organic light‐emitting transistors (OLETs). Here, a unipolar n‐type architecture suitable for the implementation of radical emitters is introduced, designed based on computational calculations. The operation of the as‐realized devices incorporating the newly synthesized [2,6‐dichloro‐4‐(2,6‐dimethoxyphenyl)phenyl](3,5‐dichloro‐4‐pyridyl) (2,4,6‐trichlorophenyl)methyl radical is investigated via transient electroluminescence measurements to demonstrate the occurrence of long‐living emission ascribed to the charge trapping mechanisms. Moreover, a comprehensive understanding of the processes governing radical‐OLET is obtained by recording complete 2D maps of both optical and electrical response of the device as a function of applied voltages. Notably, the trapping of electrons by radical moieties is demonstrated to generate a negative charge density in the emissive layer that facilitates holes to be injected: increasing the balance of opposite charge carriers, a tenfold enhancement of the external quantum efficiency (EQE) at the proper source‐drain and source‐gate voltage conditions is reported to reach a maximum EQE value of 0.2%. [ABSTRACT FROM AUTHOR]

This study focuses on the design, eco‐friendly synthesis, and characterization of several novel three‐legged triphenylamine derivatives. By performing Sonogashira couplings of functionalized aryl iodides with tris(4‐ethynylphenyl)amine in glycerol, a readily available bio‐derived solvent, we achieved the synthesis of target products in short times and high yields, up to 94 %, with consistently lower E‐factors and reduced costs compared to standard conditions using toluene as the reaction medium. The target molecules possess a D‐(π‐A)₃ or D‐(π‐D)₃ structure, where an electron‐donating core connects to three electron‐donating (D) or electron‐accepting (A) peripheral aromatic subunits through an acetylene spacer. Their main optical and electronic properties have been determined experimentally and by DFT simulations and suggest a possible implementation in energy conversion technologies such as luminescent solar concentrators (LSCs) and perovskite solar cells (PSCs). [ABSTRACT FROM AUTHOR]

The valence ionization of uracil and mixed water–uracil clusters has been studied experimentally and by ab initio calculations. In both measurements, the spectrum onset shows a red shift with respect to the uracil molecule, with the mixed cluster characterized by peculiar features unexplained by the sum of independent contributions of the water or uracil aggregation. To interpret and assign all the contributions, we performed a series of multi-level calculations, starting from an exploration of several cluster structures using automated conformer-search algorithms based on a tight-binding approach. Ionization energies have been assessed on smaller clusters via a comparison between accurate wavefunction-based approaches and cost-effective DFT-based simulations, the latter of which were applied to clusters up to 12 uracil and 36 water molecules. The results confirm that (i) the bottom-up approach based on a multilevel method [Mattioli et al. Phys. Chem. Chem. Phys. 23, 1859 (2021)] to the structure of neutral clusters of unknown experimental composition converges to precise structure–property relationships and (ii) the coexistence of pure and mixed clusters in the water–uracil samples. A natural bond orbital (NBO) analysis performed on a subset of clusters highlighted the special role of H-bonds in the formation of the aggregates. The NBO analysis yields second-order perturbative energy between the H-bond donor and acceptor orbitals correlated with the calculated ionization energies. This sheds light on the role of the oxygen lone-pairs of the uracil CO group in the formation of strong H-bonds, with a stronger directionality in mixed clusters, giving a quantitative explanation for the formation of core–shell structures. [ABSTRACT FROM AUTHOR]

We present a joint theoretical-experimental study on the inner-shell photoionization of hypoxanthine clusters in the gas phase. Simulations were performed using a computational strategy that combines molecular dynamics to explore the conformers of the clusters, density functional theory for geometry optimization and inner shell photoionization calculations. Two main intermolecular interactions are observed: hydrogen-bonds (HB) and π − π stacking. When increasing the cluster size, a combination of both kinds of interaction occurs. We show that such intermolecular interactions play a role in the chemical shift observed in X-ray photoemission spectroscopy experiments. In particular, we highlight the interplay between charge depletion and charge accumulation in regions where HBs stabilize the clusters. [ABSTRACT FROM AUTHOR]

The article offers information on the advancements in perovskite solar cells (PSCs), emphasizing their efficiency improvements over the past decade. Topics include the exploration of various strategies to enhance the quality of the perovskite layer, such as using excess precursors, additives, or passivating agents.

In dilute nitride InyGa1−yAs1−xNx alloys, a spatially controlled tuning of the energy gap can be realized by combining the introduction of N atoms—inducing a significant reduction of this parameter—with that of hydrogen atoms, which neutralize the effect of N. In these alloys, hydrogen forms N–H complexes in both Ga‐rich and In‐rich N environments. Here, photoluminescence measurements and thermal annealing treatments show that, surprisingly, N neutralization by H is significantly inhibited when the number of In‐N bonds increases. Density functional theory calculations account for this result and reveal an original, physical phenomenon: only in the In‐rich N environment, the InyGa1−yAs host matrix exerts a selective action on the N–H complexes by hindering the formation of the complexes more effective in the N passivation. This thoroughly overturns the usual perspective of defect‐engineering by proposing a novel paradigm where a major role pertains to the defect‐surrounding matrix. [ABSTRACT FROM AUTHOR]

The electronic energy levels of cyclo(glycine–phenylalanine), cyclo(tryptophan–tyrosine) and cyclo(tryptophan–tryptophan) dipeptides are investigated with a joint experimental and theoretical approach. Experimentally, valence photoelectron spectra in the gas phase are measured using VUV radiation. Theoretically, we first obtain low-energy conformers through an automated conformer–rotamer ensemble sampling scheme based on tight-binding simulations. Then, different first principles computational schemes are considered to simulate the spectra: Hartree–Fock (HF), density functional theory (DFT) within the B3LYP approximation, the quasi-particle GW correction, and the quantum-chemistry CCSD method. Theory allows assignment of the main features of the spectra. A discussion on the role of electronic correlation is provided, by comparing computationally cheaper DFT scheme (and GW) results with the accurate CCSD method. [ABSTRACT FROM AUTHOR]

Luminescent solar concentrators (LSCs) are becoming an increasingly relevant topic for building integrated photovoltaics. Even if such devices are relatively simple planar waveguides doped with a luminescent material, the achievement of relevant efficiencies requires a careful optimisation of both the matrix and the luminophore. Most of the recent literature focuses on the performance, yet the overall sustainability of the strategy is a topic at least as important. In this respect the luminophore plays a crucial role. Suitable materials must feature a near unit emission quantum yield, efficient light harvesting and a large separation between absorption and emission to reduce reabsorption losses. Due to the target application, such materials must also be readily available in large quantities through sustainable processes. Instead of going for performance first and then scaling up/optimising the synthesis, in this paper we offer a reversed perspective. We have first designed and computationally characterised materials having structural features compatible with a green chemistry synthetic approach, namely, micellar catalysis. Later, we have characterised the most promising materials in LSC devices, and we have compared their performance with commercially available, non-green chemistry compliant alternatives having similar spectral features. In the overall, we demonstrate comparable performance, but greatly improved sustainability and scalability. [ABSTRACT FROM AUTHOR]

In this study, the design, fabrication, and characterization of semi‐transparent large‐area luminescent solar concentrators (LSCs) in thin‐film configuration is reported, incorporating a novel organic luminophore (PFPBNT) emitter based on a π‐conjugated core flanked by two naphthothiophene units obtained through a chemically sustainable synthetic approach. As found experimentally and validated through computational modeling, PFPBNT exhibits aggregation‐induced emission (AIE) behavior, broad absorption in the UV–vis spectrum and significant Stokes shift (≈4632 cm–1), thereby making it an excellent candidate as luminophore in thin‐film LSCs based on a poly(methyl methacrylate) (PMMA) matrix, where it is found to show good compatibility, homogeneous distribution, and excellent photostability. After extensive device optimization, PFPBNT/PMMA LSCs with suitable luminophore concentration (12.5 wt%) showed an internal photon efficiency of 17.3% at a geometrical gain of 6.25 under solar‐simulated illumination. The size scalability of these systems was also evaluated by means of ray‐tracing simulations on devices of up to 1 m2 surface area. This work demonstrates semi‐transparent large‐area thin‐film LSCs incorporating chemically sustainable AIEgen luminophores, thus opening the way to the development of synthetically affordable, efficient, and stable emitters for the photovoltaic field. [ABSTRACT FROM AUTHOR]

In this study, the design, fabrication, and characterization of semi‐transparent large‐area luminescent solar concentrators (LSCs) in thin‐film configuration is reported, incorporating a novel organic luminophore (PFPBNT) emitter based on a π‐conjugated core flanked by two naphthothiophene units obtained through a chemically sustainable synthetic approach. As found experimentally and validated through computational modeling, PFPBNT exhibits aggregation‐induced emission (AIE) behavior, broad absorption in the UV–vis spectrum and significant Stokes shift (≈4632 cm–1), thereby making it an excellent candidate as luminophore in thin‐film LSCs based on a poly(methyl methacrylate) (PMMA) matrix, where it is found to show good compatibility, homogeneous distribution, and excellent photostability. After extensive device optimization, PFPBNT/PMMA LSCs with suitable luminophore concentration (12.5 wt%) showed an internal photon efficiency of 17.3% at a geometrical gain of 6.25 under solar‐simulated illumination. The size scalability of these systems was also evaluated by means of ray‐tracing simulations on devices of up to 1 m2 surface area. This work demonstrates semi‐transparent large‐area thin‐film LSCs incorporating chemically sustainable AIEgen luminophores, thus opening the way to the development of synthetically affordable, efficient, and stable emitters for the photovoltaic field. [ABSTRACT FROM AUTHOR]

The properties of mixed water–uracil nanoaggregates have been probed by core electron–photoemission measurements to investigate supramolecular assembly in the gas phase driven by weak interactions. The interpretation of the measurements has been assisted by multilevel atomistic simulations, based on semi-empirical tight-binding and DFT-based methods. Our protocol established a positive-feedback loop between experimental and computational techniques, which has enabled a sound and detailed atomistic description of such complex heterogeneous molecular aggregates. Among biomolecules, uracil offers interesting and generalized skeletal features; its structure encompasses an alternation of hydrophilic H-bond donor and acceptor sites and hydrophobic moieties, typical in biomolecular systems, that induces a supramolecular core–shell-like organization of the mixed clusters with a water core and an uracil shell. This structure is far from typical models of both solid-state hydration, with water molecules in defined positions, or liquid solvation, where disconnected uracil molecules are completely surrounded by water. [ABSTRACT FROM AUTHOR]

The [1]benzothieno[3,2‐b][1]benzothiophene (BTBT) planar system was used to functionalize the phthalocyanine ring aiming at synthesizing novel electron‐rich π‐conjugated macrocycles. The resulting ZnPc−BTBT and ZnPc−(BTBT)4 derivatives are the first two examples of a phthalocyanine subclass having potential use as solution‐processable p‐type organic semiconductors. In particular, the combination of experimental characterizations and theoretical calculations suggests compatible energy level alignments with mixed halide hybrid perovskite‐based devices. Furthermore, ZnPc−(BTBT)4 features a high aggregation tendency, a useful tool to design compact molecular films. When tested as hole transport materials in perovskite solar cells under 100 mA cm−2 standard AM 1.5G solar illumination, ZnPc−(BTBT)4 gave power conversion efficiencies as high as 14.13 %, irrespective of the doping process generally required to achieve high photovoltaic performances. This work is a first step toward a new phthalocyanine core engineerization to obtain robust, yet more efficient and cost‐effective materials for organic electronics and optoelectronics. [ABSTRACT FROM AUTHOR]

A tetra-n-butoxy zinc phthalocyanine (n-BuO)4ZnPc has been synthesized in a single step, starting from commercial precursors, and easily purified. The molecule can be solution processed to form an effective and inexpensive hole transport layer for organic and perovskite solar cells. These appealing features are suggested by the results of a series of chemical, optical, and voltammetric characterizations of the molecule, supported by the results of ab initio simulations. Preliminary measurements of (n-BuO)4ZnPc-methylammonium lead triiodide perovskite-based devices confirm such suggestion and indicate that the interface between the photoactive layer and the hole transporting layer is characterized by hole-extracting and electron-blocking properties, potentially competitive with those of other standards de facto in the field of organic hole transport materials, like the expensive Spiro-OMeTAD. [ABSTRACT FROM AUTHOR]

We have investigated the formation and the properties of ultrathin films of ruthenium phthalocyanine (RuPc)2 vacuum deposited on graphite by scanning tunneling microscopy and synchrotron photoemission spectroscopy measurements, interpreted in close conjunction with ab initio simulations. Thanks to its unique dimeric structure connected by a direct Ru−Ru bond, (RuPc)2 can be found in two stable rotameric forms separated by a low-energy barrier. Such isomerism leads to a peculiar organization of the molecules in flat, horizontal layers on the graphite surface, characterized by a chessboard-like alternation of the two rotamers. Moreover, the molecules are vertically connected to form π-stacked columnar pillars of akin rotamers, compatible with the high conductivity measured in (RuPc)2 powders. Such features yield an unprecedented supramolecular assembly of phthalocyanine films, which could open interesting perspectives toward the realization of new architectures of organic electronic devices. [ABSTRACT FROM AUTHOR]

The Mn4CaO5 cluster of photosystem II promotes a crucial step in the oxygenic photosynthesis, namely, the water-splitting reaction. The structure of such cluster in the S1 state of the Kok-Joliot's cycle has been recently resolved by femtosecond X-ray free-electron laser (XFEL) measurements. However, the XFEL results are characterized by appreciable discrepancies with previous X-ray diffraction (XRD), as well as with S1 models based on ab initio calculations. We provide here a unifying picture based on a combined set of DFT-based structures and molecular dynamics simulations of the S0 and S1 states. Our findings indicate that the XFEL results cannot be interpreted on the grounds of a single structure. A combination of two S1 stable isomers together with a minority contribution of the S0 state is necessary to reproduce XFEL results within 0.16 Å. [ABSTRACT FROM AUTHOR]

A number of studies have investigated the properties of monomeric and double-decker phthalocyanines (Pcs) adsorbed on metal surfaces, in view of applications in spintronics devices. In a combined experimental and theoretical study, we consider here a different member of the Pcs family, the (RuPc)2 dimer, whose structure is characterized by two paired up magnetic centers embedded in a double-decker architecture. For (RuPc)2 on Ag(111), we show that this architecture works as a preserving cage by shielding the Ru–Ru pair from a direct interaction with the surface atoms. In fact, while noticeable surface-to-molecule charge transfer occurs with the ensuing quenching of the molecular magnetic moment, such phenomena occur here in the absence of a direct Ru–Ag coupling or structural rearrangement, at variance with other Pcs and thanks to the above shielding effect. These unique properties of the (RuPc)2 architecture are expected to permit an easy control of the surface-to-molecule charge-transfer process as well as of the molecular magnetic properties, thus making the (RuPc)2 dimer a significant paradigm for innovative “cage” structures as well as a promising candidate for applications in spintronics nano or single-molecule devices. [ABSTRACT FROM AUTHOR]

Substitution of constituent atoms and/or changes of crystal structure are routinely used to tailor the fundamental properties of a semiconductor. Here, it is shown that such a tailoring can also be realized thanks to a novel hydrogen effect. Four hydrogen atoms can screen the effect the crystal potential has on a constituent cation, thus generating a solitary cation: an effectively isolated impurity, so chemically different from the unscreened constituent cations that it strongly perturbs the electronic properties of the material by increasing its fundamental band-gap energy. Such a hydrogen-induced screening effect is removed by thermal treatments, thus permitting reversible modifications of both the 'crystal chemistry' and material's properties. This phenomenon, observed in InN and other topical nitrides, should permit the development of a new class of materials as well as the fabrication of photonic devices and optical integrated circuits with distinct, tailor-made regions emitting or absorbing light, all integrated onto a monolithic semiconductor structure. [ABSTRACT FROM AUTHOR]

Atomistic simulations and experimental investigations are combined to study heterojunction interfaces of hybrid polymer solar cells, with the aim to better understand and precisely predict their photovoltaic properties. The focus is on a hybrid ternary model system based on a poly(3-hexylthiophene) (P3HT)/zinc phthalocyanine (ZnPc)/ZnO interface, in which a ZnPc interlayer is applied to improve the performance of the hybrid interface. Theoretical predictions of the ternary system are validated against the properties of a concrete P3HT/ZnPc/ZnO planar heterojunction device. The theoretical predictions closely agree with the photovoltaic properties obtained in P3HT/ZnPc/ZnO solar cells, indicating the strength of the method for modeling hybrid heterojunction interfaces. The theoretical and experimental results reveal that: i) ZnPc molecules in direct contact with a ZnO surface insert new energy levels due to a strong ZnPc/ZnO coupling, ii) electron injection from these new energy levels of ZnPc into ZnO is highly efficient, iii) the ZnPc/ZnO coupling strongly influences the energy levels of the ZnO and P3HT leading to a reduction of the open circuit voltage, and iv) charge carrier recombination at the P3HT/ZnO interface is reduced by the ZnPc interlayer. The intercalation of ZnPc leads to an increase in photocurrent as well as to an overall increase in power conversion. [ABSTRACT FROM AUTHOR]

A new unsymmetrical zinc phthalocyanine sensitizer has been synthesised. The anchoring of the molecule to nanocrystalline TiO2films is realised by a carboxylic group connected to a phenyl ethynyl moiety. Density Functional Theory (DFT) calculations show significant and positive effects of such a functionalization. Electron injection into the semiconductor and photocurrent generation in DSSC are also presented. [ABSTRACT FROM AUTHOR]

Cover Feature: [1]Benzothieno[3,2-b][1]benzothiophene-Phthalocyanine Derivatives: A Subclass of Solution-Processable Electron-Rich Hole Transport Materials (ChemPlusChem 11/2020) Keywords: hole transport; organic electronics; perovskite solar cells; photovoltaic devices; phthalocyanines EN hole transport organic electronics perovskite solar cells photovoltaic devices phthalocyanines 2358 2358 1 12/03/20 20201101 NES 201101 B The Cover Feature shows b the tetrasubstituted phthalocyanine (Pc)-benzothienobenzothiophene (BTBT) structure as an element of the geometric pattern of an azulejos mosaic. Hole transport, organic electronics, perovskite solar cells, photovoltaic devices, phthalocyanines. [Extracted from the article]

The C, N and O 1s XPS spectra of uracil clusters in the gas phase have been measured. A new bottom-up approach, which relies on computational simulations starting from the crystallographic structure of uracil, has been adopted to interpret the measured spectra. This approach sheds light on the different molecular interactions (H-bond, π-stacking, dispersion interactions) at work in the cluster and provides a good understanding of the observed XPS chemical shifts with respect to the isolated molecule in terms of intramolecular and intermolecular screening occurring after the core–hole ionization. The proposed bottom-up approach, reasonably expensive in terms of computational resources, has been validated by finite-temperature molecular dynamics simulations of clusters composed of up to fifty molecules. [ABSTRACT FROM AUTHOR]