Luminescent Solar Concentrators Based on Renewable Polyester Matrices

This study reports for the first time the use of bio‐based alternatives for PMMA as host matrix for luminescent solar concentrators (LSCs). Notably, two types of renewable polyesters were synthesized in varying molar ratios via a two‐step melt‐polycondensation reaction with dibutyl tin oxide as catalyst. The first is a homopolymer of diethyl 2,3:4,5‐di‐O‐methylene galactarate (GxMe) and isosorbide (IGPn), and the second is a random copolymer of GxMe with 1,3‐propanediol and dimethyl terephthalate (GTPn). The two polyesters were found to be optically transparent, totally amorphous with a T_g higher than 45 °C and temperature resistance comparable to PMMA. Lumogen Red (LR) and an aggregation‐induced emission (AIE) fluorophore, TPETPAFN, were utilized as fluorophores and the derived thin polymer films (25 μm) were found highly homogeneous, especially for those prepared from GTPn, possibly due to the presence of compatibilizing terephthalate units in the matrix composition and the higher molecular weight. The spectroscopic characterization and the optical efficiency determination (η_opt) evidenced LSCs performances similar or superior to those collected from LR/PMMA thin films. Noteworthy, η_opt of 7.7 % and 7.1 % were recorded for the GTPn‐based matrix containing LR and TPETPAFN, respectively, thus definitely supporting the bio‐based polyesters as renewable and highly fluorophore‐compatible matrices for high‐performance LSCs.     

Synthesis and Spectroscopic Characterization of Thienopyrazine-Based Fluorophores for Application in Luminescent Solar Concentrators (LSCs)

Organic fluorophores have found broad application as emitters in luminescent solar concentrators (LSCs) for silicon photovoltaics. In particular, the preparation of organic conjugated systems with intense light-harvesting ability, emissions in the deep-red and NIR regions, and large Stokes shift values represent a very challenging undertaking. Here, we report a simple and easy way to prepare three symmetrical donor–acceptor–donor (DAD) organic-emitting materials based on a thienopyrazine core. The central core in the three dyes was modified with the introduction of aromatic substituents, aiming to affect their optical properties. The fluorophores were characterized by spectroscopic studies. In all cases, visible-NIR emissions with large Stokes shifts were found, highlighting these molecules as promising materials for the application in LSCs.     

Efficient and Stable Thin‐Film Luminescent Solar Concentrators Enabled by Near‐Infrared Emission Perovskite Nanocrystals

A novel triphenylphosphine (TPP) treatment strategy was developed to prepare the near‐infrared emission CsPbI₃ nanocrystal (NC)‐polymer composite thin‐film luminescent solar concentrators (LSCs) featuring high absolute photoluminescence quantum yield (PLQY), low reabsorption, and high stability. The PL emission of the LSCs is centered at about 700 nm with 99.4±0.4 % PLQY and narrow full width at half maximum (FWHM) of 75 meV (30 nm). Compared with LSCs prepared with classic CsPbI₃ NCs, the stability of the LSCs after TPP treatments has been greatly improved, even after long‐term (30 days) immersion in water and strong mercury‐lamp irradiation (50 mW cm^?2). Owing to the presence of lone‐pair electrons on the phosphorus atom, TPP is also used as a photoinitiator, with higher efficiency than other common photoinitiators. Large‐area (ca. 75 cm²) infrared LSCs were achieved with a high optical conversion efficiency of 3.1 % at a geometric factor of 10.     

PL and EL behavior of near‐red luminescent metallopolymer easily prepared from phosphine‐containing copolymer and chloro{bis(1‐phenylisoquinolinato‐N,C2′)}iridium(III), and its monomeric analog

We successfully developed phosphorescent cyclometallated iridium‐containing metallopolymers, which are near‐red luminescent iridium complexes bearing phosphine‐containing copolymers used as polymer ligands, and investigated their photoluminescence and electroluminescence behavior. The phosphine copolymer ligand made from methyl methacrylate and 4‐styryldiphenylphosphine can be used as an anchor, which coordinates luminescent iridium units to form the metallopolymer easily. Organic light‐emitting diodes were fabricated from the metallopolymer and its nonpolymer analog, [IrCl(piq)₂PPh₃]. These complexes exhibited quite similar luminescence behavior, except for emission from the free‐phosphine‐units in the polymer side chain and their energy‐transferring properties from host to guest materials. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 4366–4378, 2009     

Phosphorescent organic light‐emitting diodes using an iridium complex polymer as the solution‐processible host material

We prepared an iridium polymer complex having 2‐phenylpyridine as a η²‐cyclometallated ligand, a new OLED containing a solution‐processible iridium polymer as a host, and a phosphorescent iridium complex, [Ir(piq‐^tBu)₃] as a guest. This is the first example to apply a phosphorescent iridium complex polymer to a host material in a phosphorescent OLED. A phosphine copolymer ligand made from methyl methacrylate (MMA) and 4‐styryldiphenylphosphine can be used as an anchor polymer, which coordinates to luminescent iridium units to form a host metallopolymer easily. The OLED containing the host iridium‐complex polymer film, in which the guest, 2 wt % Ir(piq‐^tBu)₃, was doped, showed red electroluminescence as a result of efficient energy transfer from the iridium polymer host to the iridium guest. The maximum current efficiency of the device was 1.00, suggesting that a soluble iridium complex polymer can be used as a solution‐processible polymer host in EL devices. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 4358–4365, 2009     

Dye-integrated cholesteric photonic luminescent solar concentrator

We have developed organic dye-integrated thin-film liquid crystalline photonic luminescent solar concentrators (LSCs), where the chirality of the liquid crystal (LC) results in the formation of a one-dimensional photonic cavity. By varying the different LSC parameters, including dye concentration, spectral position of the photonic band-gap and the LC phase, and by using spectroscopic and electrical characterisation, we have systematically studied the effects of self-absorption, incident absorption and confinement of down-converted emission on optical efficiency. Our results demonstrate that the efficiency of our LSCs is significantly enhanced in the LC phase when the photonic band-gap is at long wavelengths (>600 nm), overcoming associated low incident absorption and higher self-absorption. We reach the significant conclusion that focusing on improving the confinement of dye-emitted photons, rather than on increasing incident absorption, is a more promising route to enhancing thin-film LC-based LSC performance.     

Efficient and Stable Thin-Film Luminescent Solar Concentrators Enabled by Near-Infrared Emission Perovskite Nanocrystals

A novel triphenylphosphine (TPP) treatment strategy was developed to prepare the near-infrared emission CsPbI₃ nanocrystal (NC)-polymer composite thin-film luminescent solar concentrators (LSCs) featuring high absolute photoluminescence quantum yield (PLQY), low reabsorption, and high stability. The PL emission of the LSCs is centered at about 700 nm with 99.4±0.4 % PLQY and narrow full width at half maximum (FWHM) of 75 meV (30 nm). Compared with LSCs prepared with classic CsPbI₃ NCs, the stability of the LSCs after TPP treatments has been greatly improved, even after long-term (30 days) immersion in water and strong mercury-lamp irradiation (50 mW cm⁻²). Owing to the presence of lone-pair electrons on the phosphorus atom, TPP is also used as a photoinitiator, with higher efficiency than other common photoinitiators. Large-area (ca. 75 cm²) infrared LSCs were achieved with a high optical conversion efficiency of 3.1 % at a geometric factor of 10.     

Developing Luminescent Ratiometric Thermometers Based on a Covalent Organic Framework (COF)

Covalent Organic Frameworks (COFs), an emerging class of crystalline porous materials, are proposed as a new type of support for grafting lanthanide ions (Ln³⁺) and employing these hybrid materials as ratiometric luminescent thermometers. A TpBpy‐COF—prepared from 1,3,5‐triformylphloroglucinol (Tp) and 2,2′‐bipyridine‐5,5′‐diamine (Bpy) grafted with Eu/Tb and Dy acetylacetone (acac) complexes can be successfully used as a luminescent thermometer in the 10–360 K (Eu) and 280–440 K (Tb) ranges with good sensing properties (thermal sensitivity up to 1.403 % K^?1, temperature uncertainty δT<1 K above 110 K). For the Eu/Tb systems, we observe an unusual and rarely reported behavior, that is, no thermal quenching of the Tb³⁺ emission, a result of the absence of ion‐to‐ligand/host energy back‐transfer. The LnCOF materials proposed here could be a new class of materials employed for temperature‐sensing applications following up on the well‐known luminescent metal–organic framework thermometers.     

Temperature‐Responsive Luminescent Solar Concentrators: Tuning Energy Transfer in a Liquid Crystalline Matrix

Temperature‐responsive luminescent solar concentrators (LSCs) have been fabricated in which the Förster resonance energy transfer (FRET) between a donor–acceptor pair in a liquid crystalline solvent can be tuned. At room temperatures, the perylene bisimide (PBI) acceptor is aggregated and FRET is inactive; while after heating to a temperature above the isotropic phase of the liquid crystal solvent, the acceptor PBI completely dissolves and FRET is activated. This unusual temperature control over FRET was used to design a color‐tunable LSC. The device has been shown to be highly stable towards consecutive heating and cooling cycles, making it an appealing device for harvesting otherwise unused solar energy.     

Can computational approaches aid in untangling the inherent complexity of practical organic photovoltaic systems?

Organic materials, in particular conjugated polymers, have recently become the subject of extensive research for photovoltaic device applications. This increase of interest is primarily the result of their potentially low manufacturing cost, compatibility with flexible substrates, diverse chemical tunability, scalability, and ease of processing currently available for suitable bulk heterojunction (BHJ) construction. However, to date, these materials have not been able to exceed power conversion efficiencies (PCE) beyond 5–9%, values short of those considered commercially viable. The deficit in PCE appears to derive from a combination of physicochemical and device complexities associated with inadequate hole transport mobility, solubility and miscibility with an appropriate acceptor, narrow electronic band gap for efficient solar light harvesting, appropriate highest occupied molecular orbital (HOMO) and lowest unoccopied molecular orbital (LUMO) energies to maximize the open-circuit voltage (V_oc) and electron transfer to the acceptor, and in particular the control of the multidimensional problem of BHJ morphology. In this review article, we provide an overview of some of the recent progress toward implementing theory, modeling, and simulation approaches in combination with results from precision synthesis, characterization, and device fabrication as a mean to overcome/understand the inherent issues that limit practical applications of organic photovoltaics. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2012     

Solution processable high band gap hosts based on carbazole functionalized cyclic phosphazene cores for application in organic light‐emitting diodes

A new class of solution processable dendrimers based on cyclic phosphazene (CP) cores have been prepared and used as host materials for blue and green organic light emitting diodes (OLEDs). The dendrimers are prepared in high yield from minimal step reactions, are soluble in common solvents for solution processing, are amorphous, and have excellent thermal properties necessary for application in OLEDs. OLED efficiencies of 10.3 cd/A (4.2 lm/W) and 35.3 cd/A (33.5 lm/W) were achieved using commercially available FIrpic and Ir(mppy)₃ as blue and green phosphorescent emitters, respectively. These efficiencies were 2× higher than control devices prepared using poly(N‐vinylcarbazole), the most commonly used host material in solution processed phosphorescent OLEDs. © 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2011     

Highly Fluorescent Pyridinium Betaines for Light Harvesting

We report the findings of our experimental and theoretical investigations into the properties of pyridinium enolates and their potential utility in light‐harvesting applications, such as in luminescent solar concentrators (LSCs). We present the synthesis, structures, photophysical characterization, and wavefunction‐based quantum‐chemical studies of five cyclobetaines. The performance of an LSC device incorporating one of these cyclobetaines is shown to be comparable to state‐of‐the‐art devices.     

Polymer strategies in perovskite solar cells

Since their emergence in 2013, perovskite solar cells have reached remarkable efficiencies exceeding 22%. Such rapid development of this technology has been possible, in part, due to the feed of ideas from previous research in organic photovoltaics (OPVs) and light emitting diodes (OLEDs). This comprehensive review discusses the various polymer strategies that have led to the success of perovskite devices: from hole and electron transporting materials to polymer templating agents. This review further covers how these strategies potentially serve to overcome the two major obstacles that stand in the way of global implementation of perovskite solar cells; stability and J‐V curve hysteresis. Through reference and comparison of OPV, OLED, and perovskite technologies, we highlight the need for a unified approach to establish appropriate control systems and ageing protocols that are necessary to further research in this exciting direction. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017 , 55, 549–568     

Chaetopterus variopedatus Bioluminescence: A Review of Light Emission within a Species Complex

Chaetopterus variopedatus has been studied for over a century in terms of its physiology, ecology and life history. One focus of research is on its intrinsic bioluminescent emissions, which can be observed as a blue light emitted from the extremities of individual body segments, or as a secreted mucus. Even though research shows that C. variopedatus is a species complex miscategorized as a single species, all of the variants of this polychaete produce light, which has been investigated in terms of both physiology and biochemistry. Despite decades of study, there are still many questions about the luminescence reaction, and, as of yet, no clear function for light emission exists. This review summarizes the current knowledge on C. variopedatus luminescence in addition to briefly describing its morphology, life cycle and ecology. Possible functions for luminescence were discussed using observations of specimens found in Brazil, along with a comparison of previous studies of other luminescent organisms. Further study will provide a better understanding of how and why C. variopedatus produces luminescence, and purifying the protein and luciferin involved could lead to new bioanalytical applications, as this reaction is unique among all known luminescent systems.     

The effect of molecular structure on the secondary transitions and their influence on the decoloration kinetics of photochromic dyes in co‐polycarbonates

Photochromic dyes have restricted use in rigid polycarbonates because of slow coloration and decoloration kinetics. In this study, it is shown that the decoloration kinetics of two photochromic dyes can be controlled by tuning the chain stiffness and free volume of the host matrix. The introduction of flexible moieties in rigid BPA‐based polycarbonate chain accelerates the decoloration of these dyes whereas a rigid co‐monomer delays the decoloration kinetics. Although T_g might be used as a parameter to improve photochromism in polymer matrices, dynamic mechanical analysis demonstrates that the decoloration kinetics of the dyes in host polymer matrices having similar T_g depends primarily on the secondary relaxations and, thus, on the polymer architecture. The effect of the co‐monomer type on the characteristic ratio is also discussed underlining the potential relationship between the free volume and chain stiffness. These results open the possibility to develop transparent or semitransparent photochromic materials based on tailor‐made co‐polycarbonates. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016 , 54, 1593–1601     

Design and Development of Highly Efficient Light‐Emitting Layers in OLEDs with Dimesitylboranes: An Updated Review

With excellent luminescent properties and transport properties, triarylborane compounds containing two mesitylenes (Mes) have gained much attention for their application in OLEDs as light‐emitting layers. This study serves as an updated review summarizing recent developments in the design of fluorescent chromophores and phosphorescent host materials for OLEDs comprising small molecular compounds of dimesitylborane (BMes₂) as luminescent layers, with attention to the performance of different light‐emitting devices. Problems that need to be solved in the research and application of BMes₂ in OLEDs are presented and the application prospects of such materials are suggested.     

Tuning the performance of aqueous photovoltaic elastomer gels by solvent polarity and nanostructure development

In this study, a sulfonated pentablock ionomer is considered for use as an aqueous gel electrolyte in photovoltaic elastomer gels (PVEGs) containing photosensitive dyes. Depending on the casting solvent employed, these materials order into different nanoscale morphologies, some of which inherently consist of a continuous pathway through which ions and other polar species are able to diffuse, while others transform into continuous channels upon exposure to water. Here, we examine the effect of solvent polarity during film casting, vapor annealing, and liquid immersion on block ionomer morphology and PVEG photovoltaic performance. Casting the block ionomers from a mixed nonpolar/polar solvent promotes the formation of dispersed ion‐rich spherical microdomains. Alternatively, the use of a single polar solvent produces coexisting nonpolar cylinders and lamellae. Exposure of either morphology to polar solvent vapor causes the block ionomers to restructure into a lamellar morphology, whereas exposure of dispersed ion‐rich microdomains to water induces a transformation to an irregular morphology composed of continuous ionic channels, which provide an effective pathway for ion diffusion and, consequently, the highest photovoltaic efficiency. In addition to their photovoltaic efficacy, these aqueous gels possess improved mechanical properties (in terms of tensile strength and elastic modulus) in the presence of photosensitive dyes. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017 , 55, 85–95     

Porphyrin–diindenothieno[2,3‐b]thiophene alternating copolymer—a blue‐light harvester in ternary‐blend polymer solar cells

Porphyrin, despite chosen by Nature as light harvesting units, hasn't revealed its full potentials as a structural unit in porphyrin‐incorporated polymers (PPors). A novel PPor was synthesized to investigate the origins of the low performances of PPor‐based polymer solar cells (PSCs). The polymer features broad absorption in the blue‐light region, because the diindenothieno[2,3‐b]thiophene (DITT) unit extended the conjugation in the polymer backbone. PPor‐DITT/PC₇₁BM based PSCs have a high V_oc (0.79 V). Their low J_sc and fill factor (FF) were attributed to the un‐optimized morphology, as indicated by the photoluminescence quenching and atomic force microscopy (AFM) experiments. Using PPor‐DITT as a blue‐light harvesting dopant in an amorphous host leverage the strong 400–550 nm absorption of PPor‐DITT and circumvent the difficulties in reaching optimized morphology in the PPor/PCBM thin films. An addition of 2 wt % of PPor‐DITT in ternary‐blend PSCs resulted in a 10 % increase of external quantum efficiency (EQE) in the blue‐light region. However, in a crystalline host, the dopant decreased the crystallinity of the host and led to large drops in FF and power conversion efficiencies (PCEs). The study provides an alternative route and expands the application of PPors in PSCs as a blue‐light harvester in ternary‐blend PSCs using amorphous polymers as host. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Luminescent poly(phenylene vinylene) derivatives with m‐terphenyl or 2,6‐diphenylpyridine kinked segments along the main chain: Synthesis,characterization, and stimulated emission

Two new poly(phenylene vinylene)s containing m‐terphenyl or 2,6‐diphenylpyridine kinked units along the main chain were synthesized and were used as luminescent and laser materials. They were prepared from Heck coupling of 2,5‐didodecyloxy‐1,4‐divinylbenzene with 4,4″‐dibromo‐3′‐phenyl‐m‐terphenyl or 2,6‐di(4‐bromophenyl)‐4‐phenylpyridine. The kinked units along the main chain caused a partial interruption of the conjugation leading to emission at a shorter wavelength as compared with poly(p‐phenylene vinylene). The polymers presented blue‐green emission in solution and green‐yellow emission in the solid state with photoluminescence maxima at 465–497 and 546–550 nm, respectively. Polymer containing 2,6‐diphenylpyridine segments emitted at a longer wavelength than that containing m‐terphenyl and displayed higher quantum yields in solution (0.61 and 0.40, respectively). The influence of the solvent and polymer concentration on the photoluminescence characteristics was investigated. The photoluminescence properties of protonated polymer containing 2,6‐diphenylpyridine segments were investigated both in solution and in film. Amplified spontaneous emission and tunable laser action were also obtained from the two polymers. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2214–2224, 2004     

Synthesis of phosphorescent iridium-containing acrylic monomers and their room-temperature polymerization by Cu(0)-RDRP

A series of acrylic monomers based on cyclometalated iridium(III) complexes have been synthesized based on common phosphorescent emitters for organic light-emitting diodes. A simple room-temperature polymerization procedure for these materials was developed using Cu(0) reversible deactivation radical polymerization, providing polymers with low dispersities of 1.08–1.14 at conversions from 81 to 93% when the Ir complexes are copolymerized with a carbazole-based acrylic host. These methods were also found to be suitable for the preparation of high-molecular-weight polymers with M _n approaching 40,000 Da, as well as block copolymers formed in one pot from the chain extension of methyl acrylate. This scalable room-temperature synthesis of iridium-containing copolymers and block copolymers provides a useful route to optoelectronic materials, which we anticipate can be readily adapted to a broad range of acrylic metallopolymers. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018 , 56, 2539–2546