Polymer solar cells (PSCs) based on non-fullerene acceptors have the advantages of synthetic versatility, strong absorption ability, and high thermal stability. These characteristics result in ...impressive power conversion efficiency values, but to further push both the performance and the stability of PSCs, the insertion of appropriate interlayers in the device structure remains mandatory. Herein, a naphthalene diimide-based cathode interlayer (NDI-OH) is synthesized with a facile three-step reaction and used as a cathode interlayer for fullerene and non-fullerene PSCs. This cationic polyelectrolyte exhibited good solubility in alcohol solvents, transparency in the visible range, self-doping behavior, and good film forming ability. All these characteristics allowed the increase in the devices’ power conversion efficiencies (PCE) both for fullerene and non-fullerene-based PSCs. The successful results make NDI-OH a promising cathode interlayer to apply in PSCs.
Impressive advancements in solution‐processed bulk heterojunction (BHJ) solar cells have been driven to a large extent by the rational design of conjugated polymers as photoactive donors. These ...achievements have been obtained without paying much attention to green metrics parameters (such as E factor) and to the increasing synthetic complexity (SC), which is a bottleneck for industrial scalability. In this context, a novel donor copolymer (PBDT3T) based on benzodithiophene and terthiophene building blocks with ester functionalities is synthesized. The 26‐fold‐reduced E factor for the benzodithiophene monomer synthesis and the SC index of 24 for PBDT3T, much lower compared with benchmark donor polymers, provide a hint for good scalability, sustainability, and low costs. PBDT3T features a relatively wide optical bandgap and a deep highest occupied molecular orbital (HOMO), meeting the requirements for suitable donor material in both fullerene and nonfullerene‐based solar cells. PBDT3T is studied in binary and ternary blend, using PC71BM and ITIC as acceptors. The best performances are obtained in the ternary blend devices, reaching power conversion efficiency (PCE) values of 7.14%. Trade‐off considerations between PCE and SC make PBDT3T promising on an industrial perspective.
A novel ester‐substituted benzodithiophene–terthiophene copolymer (PBDT3T) exhibiting a low synthetic complexity (six synthetic steps) is prepared and tested as the donor material in polymer solar cells. Devices with conventional architecture based on ternary blends with ITIC and PC71BM acceptors exhibit power conversion efficiencies of over 7%., without the use of high‐boiling‐point solvent additives.
An efficient continuous synthesis of nanolatex was achieved in water using a single-lane photochemical microreactor combined with an energy-saving and safe UV fluorescent lamp. Acrylate and thiol-ene ...miniemulsions were polymerized in high yields at low irradiance (3 mW cm
−2
) upon controlling droplet size, temperature and residence time.
The first study on the second-order NLO properties of unconventional push–pull systems constituted by asymmetrically monoaryl-substituted thioalkyl porphyrazines, carried out by EFISH measurements ...and DFT calculations, is here reported. The results obtained show that the porphyrazine macrocycle behaves as a better electron donor and acceptor with respect to structurally similar porphyrin and phthalocyanine tetrapyrroles. Noteworthy, the highest quadratic hyperpolarizability (β1907) values are displayed by the pyrene-substituted thioalkyl porphyrazines, both as free-base and as PdII complex, without the presence of either electron-withdrawing or electron-donating groups. In these cases, the pyrene moiety behaves as an electron-donating group, giving rise to charge transfer HOMO–LUMO electronic transitions. These outcomes show, for the first time, the great potential of the thioalkyl porphyrazine macrocycles for second-order NLO applications. Moreover, the hydroxyphenyl-substituted porphyrazine 2 dye has been also tested as a sensitizer in a TiO2–DSSC, representing the second example reported so far of a DSSC with thioalkyl porphyrazines.
The continuous photopolymerization of acrylate and methacrylate monomer miniemulsions (25% solids content) is investigated at room temperature in a compact helix minireactor. Using n‐butyl acrylate, ...the process yields 95% conversion after only 27 s residence time, and gel‐free high‐molecular‐weight products. Under optimized conditions, a 25‐fold increase in efficiency is obtained when compared to a batch photopolymerization. The reaction set‐up offers a frugal process because of moderate irradiance (2.6 mW cm−2), photoinitiator concentration (0.75 wt%), and low‐power UV‐A fluorescent lamp.
A novel continuous radical photopolymerization process enables to convert acrylate monomer emulsion with surprisingly high efficiency. The combination of a photochemical minireactor, the resulting very short polymerization times, low costs of production, and the simplicity of the equipment may be of interest to change the way emulsion polymerization is performed both at research and industrial levels.
The impact of organic light-emitting diodes (OLEDs) in modern life is witnessed by their wide employment in full-color, energy-saving, flat panel displays and smart screens; a bright future is ...likewise expected in the field of solid-state lighting. Cyclometalated iridium complexes are the most used phosphorescent emitters in OLEDs because of their widely tunable photophysical properties and their versatile synthesis. Blue-emitting OLEDs suffer from intrinsic instability issues hampering their long-term stability. Backed by computational studies, in this work, we studied the sky-blue emitter bis2-(4,6-difluorophenyl)pyridyl-C 2,N(picolinato)iridium(III) (FIrpic) in both ex situ and in situ degradation experiments combining complementary, mutually independent experiments including chemical metathesis reactions, in liquid phase and solid state, thermal and spectroscopic studies, and liquid chromatography–mass spectrometry investigations. We developed a straightforward protocol to evaluate the degradation pathways in iridium complexes, finding that FIrpic degrades through the loss of the picolinate ancillary ligand. The resulting iridium fragment was than efficiently trapped “in situ” as BPhen derivative 1. This process is found to be well mirrored when a suitably engineered, FIrpic-based OLED is operated and aged. In this paper, we (i) describe how it is possible to effectively study OLED materials with a small set of readily accessible experiments and (ii) evidence the central role of host matrix in trapping experiments.
Trees are emblems of wisdom, power and prosperity, and recall a growing force connecting different elements (earth, air, water and lives). Philosophers consider trees to be witnesses of the evolution ...of humans and the planet. In the scientific world the “tree of life” is a metaphor for the connection between complementary fields and expertise. This image communicates that, through appropriate collaborations, interesting research results (the fruits of a tree) can be achieved from which humans could benefit. More information can be found in the Research Article by A. Bossi, E. Licandro and co‐workers (DOI: 10.1002/chem.202300339). Image by Dr. Sara Grecchi, Department of Chemistry, University of Milan.
Structure‐property correlations in the thiahelicene family are often not trivial beacuse most of the functional groups present on the helical scaffold modify the conjugation size of the π‐system. ...Selecting fluorine‐containing groups to provide strong inductive effects without interacting with low‐lying orbitals of the system could be the way to overcome the issue. Here we report a study on three fluorine‐functionalized tetrathia7helicenes, highlighting interesting correlations between the position of the functional groups and the conjugated skeleton properties. Helicenes Heli‐F2 and Heli‐CF‐F2 were prepared by photoinduced isomerization‐electrocyclization (the Mallory photocyclization) of the corresponding fluorinated benzodithienyl‐ethenes Alk‐F2 and Alk‐CF‐F2, which were prepared in high yields through stereo‐conservative Stille reaction. Notably these helicenes were found to display green phosphorescence around 530–550 nm, and the studies suggest an efficient spin‐orbit coupling mechanism in these high‐energy triplet nonplanar conjugated molecules. Both helicenes and their precursors were thoroughly characterized by means of optical and electrochemical measurements, while DFT calculations enable a rationale on their structure‐property correlations to be defined.
Cyclometalated Ir(III) compounds are the preferred choice as organic emitters in organic light-emitting diodes. In practice, the presence of the transition metal surrounded by carefully designed ...ligands allows fine-tuning of the emission frequency as well as good efficiency of the device. To support the development of new compounds, experimental measurements are generally compared with absorption and emission spectra obtained from ab initio calculations. The standard approach for these calculations is time-dependent density functional theory (TDDFT) with a hybrid exchange–correlation functional like B3LYP. Because of the size of these compounds, the application of more complex quantum chemistry approaches can be challenging. In this work, we used many-body perturbation theory approaches, in particular the GW approximation with the Bethe–Salpeter equation (BSE) implemented in Gaussian basis sets, to calculate the quasiparticle properties and the absorption spectra of six cyclometalated Ir(III) complexes, going beyond TDDFT. In the presented results, we compared standard TDDFT simulations with BSE calculations performed on top of perturbative G0W0 and accounting for eigenvalue self-consistency. Moreover, in order to investigate in detail the effect of the DFT starting point, we concentrated on Ir(ppy)3 and performed GW-BSE simulations starting from different DFT exchange–correlation potentials.
Three NIR‐emitting neutral IrIII complexes Ir(iqbt)2(dpm) (1), Ir(iqbt)2(tta) (2), and Ir(iqbt)2(dtdk) (3) based on the 1‐(benzobthiophen‐2‐yl)‐isoquinolinate (iqtb) were synthesized and ...characterized (dpm=2,2,6,6‐tetramethyl‐3,5‐heptanedionate; tta=2‐thienoyltrifluoroacetonate; dtdk=1,3‐di(thiophen‐2‐yl)propane‐1,3‐dionate). The compounds emit between λ=680 and 850 nm with high luminescence quantum yields (up to 16 %). By combining electrochemistry, photophysical measurements, and computational modelling, the relationship between the structure, energy levels, and properties were investigated. NIR‐emitting, solution‐processed phosphorescent organic light‐emitting devices (PHOLEDs) were fabricated using the complexes. The devices show remarkable external quantum efficiencies (above 3 % with 1) with negligible efficiency roll‐off values, exceeding the highest reported values for solution‐processible NIR emitters.
Let's glow: Heteroleptic benzobthiophenyl isoquinolinate IrIII complexes with diketonate ancillary ligands of increasing conjugation were prepared. The compounds are NIR emissive with high emission quantum yields (up to 16 %). A solution‐processed OLED fabricated with one of the complexes demonstrates a remarkable external quantum efficiency (EQE) of more than 3 % with negligible efficiency roll‐off.
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