Luminescent Solar Concentrators Based on Renewable Polyester Matrices

A comprehensive dataset of photonic features on spectral converters for energy harvesting

Building integrated photovoltaics is a promising strategy for solar technology, in which luminescent solar concentrators (LSCs) stand out. Challenges include the development of materials for sunlight harvesting and conversion, which is an iterative optimization process with several steps: synthesis, processing, and structural and optical characterizations before considering the energy generation figures of merit that requires a prototype fabrication. Thus, simulation models provide a valuable, cost-effective, and time-efficient alternative to experimental implementations, enabling researchers to gain valuable insights for informed decisions. We conducted a literature review on LSCs over the past 47 years from the Web of ScienceTM Core Collection, including published research conducted by our research group, to gather the optical features and identify the material classes that contribute to the performance. The dataset can be further expanded systematically offering a valuable resource for decision-making tools for device design without extensive experimental measurements.

Facile and Efficient Production of Biomass-Derived Isosorbide Dioxides via Epoxidation Using In situ-generated DMDO under Ultrasonication

Herein, we present a facile synthetic process for producing biomass-derived isosorbide (ISB) dioxides using dimethyl dioxirane (DMDO) as an efficient oxidizing agent, which was generated in situ from acetone and KHSO5 . To achieve high conversion and product yield, the KHSO5 concentration, KHSO5 flow rate, and reaction temperature were optimized. Under the optimal conditions, rapid and efficient epoxidation using the in situ-generated DMDO was observed under ultrasonication, yielding the desired product within 35 min at 0 °C. This study offers a convenient and efficient method for generating biomass-derived ISB building blocks, which have significant potential for the fabrication of bioplastics.

Effect of Polymer Composition on the Optical Properties of a New Aggregation-Induced Emission Fluorophore: A Combined Experimental and Computational Approach

Nowadays, fluorophores with a tetraphenylethylene (TPE) core are considered interesting due to the aggregation-induced emission (AIE) behavior that enables their effective use in polymer films. We propose a novel TPE fluorophore (TPE-BPAN) bearing two dimethylamino push and a 4-biphenylacetonitrile pull moieties with the typical AIE characteristics in solution and in the solid state, as rationalized by DFT calculations. Five different host polymer matrices with different polarity have been selected: two homopolymers of poly(methylmethacrylate) (PMMA) and poly(cyclohexyl methacrylate) (PCHMA) and three copolymers at different compositions (P(MMA-co-CHMA) 75:25, 50:50, and 25:75 mol%). The less polar comonomer of CHMA appeared to enhance TPE-BPAN emission with the highest quantum yield (QY) of about 40% measured in P(MMA-co-CHMA) 75:25. Further reduction in polymer polarity lowered QY and decreased the film stability and adhesion to the glass surface. LSC performances were not significantly affected by the matrix's polarity and resulted in around one-third of the state-of-the-art due to the reduced QY of TPE-BPAN. The theoretical investigation based on density functional theory (DFT) calculations clarified the origin of the observed AIE and the role played by the environment in modulating the photophysical behavior.

Minimizing Scaling Losses in High-Performance Quantum Dot Luminescent Solar Concentrators for Large-Area Solar Windows

While luminescent solar concentrators (LSCs) have been researched for several decades, there is still a lack of commercially available systems, mostly due to scalability, performance, aesthetics, or some combination of these challenges. These obstacles can be overcome by the systematic optimization of a laminated glass LSC design, demonstrated herein. In particular, we first show that it is possible to improve optical and electrical efficiencies of an LSC by fine-tuned optimization of the constituent fluorophore-containing interlayer resin. Further still, an increased understanding of commercially available solar cells allows us to establish a direct correlation between the device's optical and electrical efficiency. Next, optical characterization of LSCs of varying sizes allows us to elucidate the main loss mechanisms in our LSCs, as well as ways to mitigate them. Altogether these optimization steps create opportunities for high-performance multi-interlayer LSC devices with demonstrated electrical power conversion efficiency as high as 1.1% to 4.9% at visual light transmission of 74% to 5%. Furthermore, careful examination of different blue-color (red-band absorbing) dyes provides a path for color-tunability of LSC windows toward neutral regimes. Design iterations of multiple device form factors enabled a color-neutral prototype without significant performance losses by separating color-neutralizing and LSC layers into different panes of an insulated glass unit. This work demonstrates the importance of LSC design optimization in achieving high-performance solar window technology with commercially acceptable aesthetics.

Thin-Film Luminescent Solar Concentrator Based on Intramolecular Charge Transfer Fluorophore and Effect of Polymer Matrix on Device Efficiency

Luminescent solar concentrators (LSCs) provide a transformative approach to integrating photovoltaics into a built environment. In this paper, we report thin-film LSCs composed of intramolecular charge transfer fluorophore (DACT-II) and discuss the effect of two polymers, polymethyl methacrylate (PMMA), and poly (benzyl methacrylate) (PBzMA) on the performance of large-area LSCs. As observed experimentally, DACT-II with the charge-donating diphenylaminocarbazole and charge-accepting triphenyltriazine moieties shows a large Stokes shift and limited re-absorption losses in both polymers. Our results show that thin-film LSC (10 × 10 × 0.3 cm³) with optimized concentration (0.9 wt%) of DACT-II in PBzMA gives better performance than that in the PMMA matrix. In particular, optical conversion efficiency (η_opt) and power-conversion efficiency (η_PCE) of DACT-II/PBzMA LSC are 2.32% and 0.33%, respectively, almost 1.2 times higher than for DACT-II/PMMA LSC.

Catalyst-Free Spontaneous Polymerization with 100% Atom Economy: Facile Synthesis of Photoresponsive Polysulfonates with Multifunctionalities

Photoresponsive polymers have attracted extensive attention due to their tunable functionalities and advanced applications; thus, it is significant to develop facile in situ synthesis strategies, extend polymers family, and establish various applications for photoresponsive polymers. Herein, we develop a catalyst-free spontaneous polymerization of dihaloalkynes and disulfonic acids without photosensitive monomers for the in situ synthesis of photoresponsive polysulfonates at room temperature in air with 100% atom economy in high yields. The resulting polysulfonates could undergo visible photodegradation with strong photoacid generation, leading to various applications including dual-emissive or 3D photopatterning, and practical broad-spectrum antibacterial activity. The halogen-rich polysulfonates also exhibit a high and photoswitched refractive index and could undergo efficient postfunctionalizations to further expand the variety and functionality of photoresponsive heteroatom-containing polyesters.

High-Performance Luminescent Solar Concentrators Based on Poly(Cyclohexylmethacrylate) (PCHMA) Films

In this study, we report on the use of poly(cyclohexylmethacrylate) (PCHMA) as an alternative to the commonly used poly(methylmethacrylate) (PMMA) for the design of efficient luminescent solar concentrators (LSCs). PCHMA was selected due to its less polar nature with respect to PMMA, a characteristic that was reported to be beneficial in promoting the fluorophore dispersibility in the matrix, thus maximizing the efficiency of LSCs also at high doping. In this sense, LSC thin films based on PCHMA and containing different contents of Lumogen F Red 305 (LR, 0.2–1.8 wt%) demonstrated optical efficiencies (η_opt) comprising between 9.5% and 10.0%, i.e., about 0.5–1% higher than those collected from the LR/PMMA systems. The higher LR/polymer interactions occurred using the PCHMA matrix maximized the solar harvesting characteristics of the fluorophore and limited the influence of the adverse dissipative phenomena on the fluorophore quantum efficiency. These effects were also reflected by varying the LSC film thickness and reaching maximum η_opt of about 11.5% in the case of PCHMA films of about 30 µm.

Luminescent Solar Concentrators from Waterborne Polymer Coatings

This study reports for the first time the use of waterborne polymers as host matrices for luminescent solar concentrators (LSCs). Notably, three types of waterborne polymer dispersions based either on acrylic acid esters and styrene (Polidisp® 7602), acrylic and methacrylic acid esters (Polidisp® 7788) or aliphatic polyester-based polyurethane (Tecfin P40) were selected as amorphous coatings over glass substrates. Water soluble Basic Yellow 40 (BY40) and Disperse Red 277 (DR277) were utilized as fluorophores and the derived thin polymer films (100 μm) were found homogeneous within the dye range of concentration investigated (0.3–2 wt.%). The optical efficiency determination (ηopt) evidenced LSCs performances close to those collected from benchmark polymethylmethacrylate (PMMA) thin films and Lumogen Red F350 (LR) with the same experimental setup. Noteworthy, maximum ηopt of 9.5 ± 0.2 were recorded for the Polidisp® 7602 matrix containing BY40, thus definitely supporting the waterborne polymer matrices for the development of high performance and cost-effective LSCs.

Tunable Aggregation-Induced Emission of Imidazole Hydrazones by pH and Anions

Aggregation-induced emission (AIE) materials have drawn great attention for applications as organic light-emitting diodes (OLED) and probes. The applications are, however, restricted by the complex syntheses and hydrophobic properties. Herein, a one-step synthesis of an AIE material based on imidazole hydrazone is assessed. Protonation of the imidazole-H leads to emission color change from yellow to green in the solid state. The emission color is recovered upon imidazole-H⁺ deprotonation. Moreover, the emission wavelength shifts from 532 to 572 nm by anion exchange. In addition, an enhanced emission (Φ_F up to 22.6 %) was obtained with the Br^- anion compared with NTf₂ ^- , SbCl₅ ^- , PF₆ ^- , and OTf^- anions. X-ray crystallography studies together with theoretical calculations show that the enhanced emission of hydrazone salts arises from strong hydrogen bonding between the hydrazone proton and the halide ion (Cl^- or Br^- ).

Mechanochromic Fluorescent Polymers with Aggregation-Induced Emission Features

Mechanochromic polymers are defined as materials that are able to detect a mechanical stress through an optical output. This feature has evoked a growing interest in the last decades, thanks to the progress of chromogenic molecules whose optical characteristics and chemical functionalities allow their effective insertion in many thermoplastic and thermoset matrices. Among the different types of fluorogenic probes able to detect mechanical solicitations, those with aggregation-induced emission (i.e., AIEgens) have attracted tremendous interest since their discovery in 2001. In the present review, the main principles behind the AIEgens working behavior are introduced along with the current state of knowledge concerning the design and preparation of the derived mechanochromic fluorescent polymers. Examples are provided concerning the most ingenious solution for the preparation of chromogenic materials, starting from different types of commodity plastics or synthetic polymers and combined with the latest AIE technology to provide the most sensitive response to mechanical stress.