Photoactive Systems Research Articles

Chlorinated Polythiophene‐Based Donors with Reduced Energy Loss for Organic Solar Cells

Comprehensive SummaryThe industrialization of organic solar cells (OSCs) faces challenges due to complex synthesis routes and high costs of organic photovoltaic materials. To address this, we designed and synthesized a series of polythiophene‐based donor materials, PTVT‐T‐xCl (20%Cl, 50%Cl and 100%Cl), by introducing different degrees of chlorine substitution within their conjugated skeletons. The incorporation of chlorine atoms does not change the planar conformation of the conjugated main chain of the control polymer, PTVT‐T, but effectively reduces their HOMO energy levels (≤ –5.3 eV) and alters the crystallinity of the polymers. In addition, when preparing OSC by blending with non‐fused electron acceptor A4T‐16, the non‐radiative energy loss of the three photovoltaic devices gradually decreased with the increase of chlorine content (0.343, 0.278 and 0.189 eV, respectively). Notably, PTVT‐T‐20%Cl exhibited a more moderate nanoscale phase separation with the acceptor, leading to efficient exciton dissociation, lower bimolecular recombination, and thus a favorable current in the OSCs. Consequently, the photovoltaic device based on PTVT‐T‐20%Cl:A4T‐16 achieved a remarkable photovoltaic efficiency of 11.8%. In addition, the PTVT‐T‐xCl series polymers show much lower material‐only‐cost (MOC) values than the other reported photoactive material systems. This work provides the way for the development of low‐cost photovoltaic materials and the industrial application of OSC, overcoming previous limitations posed by high energy losses in polythiophene‐based donors.

Tracking Microenvironmental Response on Self-Assembled Phthalocyanine Systems - Adaptive and Non-Adaptive Antibacterial Photosensitization.

Self-assembly has proven to be one of the effective methods for the formation of nanoscale therapeutics without the need to use nanodelivery systems. Such minimal models of supramolecular systems formed from amphiphilic photosensitizers (PS) have recently emerged as a new class of photoactive systems, providing unique and in some cases superior activities. Although the mechanism of photogenerated reactive oxygen species (ROS) in such systems is studied and to a certain extent understood, there are very limited studies investigating the influence of intricate environmental factors, including those occurring in the cellular environment, on the self-assembly and thus the activity of the system. Understanding the optimal conditions for the formation of active PS aggregates is an important area of research in the field of photodynamic therapy (PDT), as it is directly linked to the optimal treatment dose. In this study, we describe the synthesis, self-assembly properties, photophysical characterization, and photobiological efficacy of structurally closely related low-symmetry phthalocyanine derivatives. Studying the decay behavior of the PS fluorescence lifetime in the presence of molecular crowders and different bacterial strains, we found that certain derivatives exhibited adaptive behavior and change in activity, while others demonstrated non-adaptive characteristics.

Photo‐responsive systems based on anisotropic composites of poly(N‐vinyl formamide) and active fillers using directional freezing combined with gamma irradiation crosslinking

AbstractThis study deals with the fabrication of smart anisotropic composite systems capable of reacting to light stimulus and reversibly providing significant change in the length. Surface‐modified carbon nanotubes (CNTs) and poly(pyrrole) (PPy) nanotubes were used as photoactive fillers. Anisotropic composites containing these fillers and poly(N‐vinyl formamide) (PNVF) matrix were fabricated using a directional freezing technique with freezable monomer, N‐vinyl formamide (NVF), as structure guiding medium and subsequent gamma irradiation polymerization and crosslinking technique. The dielectric properties showed that there is the presence of both relaxation processes α and β, which are significantly influenced by the presence of photoactive filler. The anisotropic distribution of fillers in samples was confirmed using microscopical, electrical conductivity and mechanical properties analysis. Finally, the photoactuation capabilities were investigated and showed enhanced photoactive response for the anisotropic system in the change in the length up to 54 μm after irradiation at 627 nm with a very low light intensity of 6 mW cm−2 in a fully reversible and repeatable manner. The simple, affordable, and industrially scalable fabrication technique opens an avenue for smart anisotropic photoactive composite systems.

(Invited) Design of Photoactive Inorganic Nanomaterials for Environmental Challenges

Nowadays, one of the main technological challenges that we are facing is the ability to provide a sustainable supply of clean energy and, among all renewable sources, solar energy displays the greatest potential. Recently, the development of novel synthetic strategies has led to the preparation of nanostructured materials displaying unique properties compared to the bulk counterpart systems, with controlled and tunable morphologies able to enhance the activity and selectivity of a catalytic process. In particular, nanostructured materials synthesized via the bottom–up approach present an opportunity for future generation manufacturing of devices.This talk will focus on the importance of tuning the morphological features of a catalyst as a strategy to improve its optical and photocatalytic properties, focusing on how rationally designing inorganic materials at the nanoscale can lead to morphologies and structures suitable to enhance the performance of industrially and environmentally important processes. The talk will discuss some environmental applications that can be addressed by photoactive multi-component oxide systems synthesized via the bottom–up approach, highlighting their structure-reactivity relationship. Water contamination, in particular, is one of the upfront issues to be solved and complex organic molecules and pharmaceuticals, including antibiotics, are gaining attention due to their abuse and their low degradability. Photocatalytic drugs degradation will be presented as a successful case history [1-3] to provide inspiration to produce cheap, environmentally friendly, stable, and efficient photocatalysts, which hold a great potential for the development of new technologies not only for water remediation applications but also for energy applications in the field of solar fuel production.[1] E. Moretti, L. Storaro, A. Talon, P. Riello, A. Infantes Molina, E. Rodríguez-Castellón, Appl. Catal. B: Environmental 168 (2015) 385.[2] M. Telkhozhayeva, B. Hirsch, R. Konar, E. Teblum, R. Lavi, M. Weitman, B. Malik, E. Moretti, G.D. Nessim, Appl. Catal. B: Environmental 318 (2022) 121872.[3] L. Liccardo, M. Bordin, P.M. Sheverdyaeva, M. Belli, P. Moras, A. Vomiero, E. Moretti, Adv. Funct. Mater. 33 (2023) 2212486.

Bis-azopyrazole Photoswitches for Efficient Solar Light Harvesting.

Although natural sunlight is one of the most abundant and sustainable energy resources, only a fraction of its energy is currently harnessed and utilized in photoactive systems. The development of molecular photoswitches that can be directly activated by sunlight is imperative for unlocking the full potential of solar energy and addressing the growing energy demands. Herein, we designed a series of 2-amino-1,3-bis-azopyrazoles featuring a coupled πn system, resulting in a pronounced redshift in their spectral absorption, reaching up to 661 nm in the red region. By varying the amino substituents of these molecules, highly efficient E→Z photoisomerization under unfiltered sunlight can be achieved, with yields of up to 88.4 %. Moreover, the Z,Z-isomers have high thermal stability with half-lives from days to years at room temperature. The introduction of ortho-amino substitutions and meta-bisazo units leads to a reversal of the n-π* and πn-π* transitions on the energy scale. This change provides a new perspective for further tuning the visible absorption of azo-switches by utilizing the πn-π* band instead of the conventional n-π* band. These results suggest that photoresponsive systems can be powered by sunlight instead of traditional artificial lights, thereby paving the way for sustainable smart materials and devices.

Bis‐azopyrazole Photoswitches for Efficient Solar Light Harvesting

AbstractAlthough natural sunlight is one of the most abundant and sustainable energy resources, only a fraction of its energy is currently harnessed and utilized in photoactive systems. The development of molecular photoswitches that can be directly activated by sunlight is imperative for unlocking the full potential of solar energy and addressing the growing energy demands. Herein, we designed a series of 2‐amino‐1,3‐bis‐azopyrazoles featuring a coupled πn system, resulting in a pronounced redshift in their spectral absorption, reaching up to 661 nm in the red region. By varying the amino substituents of these molecules, highly efficient E→Z photoisomerization under unfiltered sunlight can be achieved, with yields of up to 88.4 %. Moreover, the Z,Z‐isomers have high thermal stability with half‐lives from days to years at room temperature. The introduction of ortho‐amino substitutions and meta‐bisazo units leads to a reversal of the n–π* and πn–π* transitions on the energy scale. This change provides a new perspective for further tuning the visible absorption of azo‐switches by utilizing the πn–π* band instead of the conventional n–π* band. These results suggest that photoresponsive systems can be powered by sunlight instead of traditional artificial lights, thereby paving the way for sustainable smart materials and devices.

Solar Azo-Switches for Effective E→Z Photoisomerization by Sunlight.

Natural photoactive systems have evolved to harness broad-spectrum light from solar radiation for critical functions such as light perception and photosynthetic energy conversion. Molecular photoswitches, which undergo structural changes upon light absorption, are artificial photoactive tools widely used for developing photoresponsive systems and converting light energy. However, photoswitches generally need to be activated by light of specific narrow wavelength ranges for effective photoconversion, which limits their ability to directly work under sunlight and to efficiently harvest solar energy. Here, focusing on azo-switches-the most extensively studied photoswitches, we demonstrate effective solar E→Z photoisomerization with photoconversions exceeding 80 % under unfiltered sunlight. These sunlight-driven azo-switches are developed by rendering the absorption of E isomers overwhelmingly stronger than that of Z isomers across a broad ultraviolet to visible spectrum. This unusual type of spectral profile is realized by a simple yet highly adjustable molecular design strategy, enabling the fine-tuning of spectral window that extends light absorption beyond 600 nm. Notably, back-photoconversion can be achieved without impairing the forward solar isomerization, resulting in unique light-reversible solar switches. Such exceptional solar chemistry of photoswitches provides unprecedented opportunities for developing sustainable light-driven systems and efficient solar energy technologies.

Solar Azo‐Switches for Effective E→Z Photoisomerization by Sunlight

AbstractNatural photoactive systems have evolved to harness broad‐spectrum light from solar radiation for critical functions such as light perception and photosynthetic energy conversion. Molecular photoswitches, which undergo structural changes upon light absorption, are artificial photoactive tools widely used for developing photoresponsive systems and converting light energy. However, photoswitches generally need to be activated by light of specific narrow wavelength ranges for effective photoconversion, which limits their ability to directly work under sunlight and to efficiently harvest solar energy. Here, focusing on azo‐switches—the most extensively studied photoswitches, we demonstrate effective solar E→Z photoisomerization with photoconversions exceeding 80 % under unfiltered sunlight. These sunlight‐driven azo‐switches are developed by rendering the absorption of E isomers overwhelmingly stronger than that of Z isomers across a broad ultraviolet to visible spectrum. This unusual type of spectral profile is realized by a simple yet highly adjustable molecular design strategy, enabling the fine‐tuning of spectral window that extends light absorption beyond 600 nm. Notably, back‐photoconversion can be achieved without impairing the forward solar isomerization, resulting in unique light‐reversible solar switches. Such exceptional solar chemistry of photoswitches provides unprecedented opportunities for developing sustainable light‐driven systems and efficient solar energy technologies.

Unveiling the future of environmental solutions: S-g-C3N4/Te-doped metal oxides (ZnO, Mn3O4 & SnO2) as game-changers in photocatalytic and antibacterial technologies

Researchers aim to develop photoactive systems to address critical environmental challenges, presenting a significant ongoing challenge. This study emphasizes the construction of pure metal oxide NPs (ZnO, Mn3O4, and SnO2), tellurium-doped metal oxides, and composite materials of graphitic carbon nitride/tellurium-doped metal oxides to enhance photocatalytic performance in methylene blue (MB) degradation under natural sunlight. Various characterization techniques, XRD, EDX, SEM, FTIR and UV–Vis Spectroscopy, were employed to analyze the structure, shape, and optical features of the materials. The photocatalytic degradation order for MB was determined to be pure and doped ZnO > pure & doped SnO2 > pure & doped Mn3O4. ZnO NPs exhibited the highest photocatalytic degradation at 98 %, accredited to their higher crystallinity, insignificant surface area and reduced particle dimension. Pure and doped ZnO NPs demonstrated the maximum zone of inhibition, reaching 39.5 mm. Consequently, S-g-C3N4/Te-ZnO emerges as the most promising material, serving as both a photocatalytic and antibacterial agent.

Synthesis, Photophysical, and AIE Properties of 2H-Imidazole-Derived Push-Pull Fluorophores

AbstractA four-stage method for the synthesis of 2H-imidazole-derived push-pull fluorophores was developed. The synthesized compounds are characterized by absorption in the range of 250–400 nm, emission of up to 617 nm, and quantum yields of up to 99%. Compounds bearing a tetraphenylethylene fragment demonstrated the AIE effect in a solution with a water fraction fw >90% and significant increase in the emission intensity of up to 20 times and quantum yields of up to 22%. The ICT states for these fluorophores were confirmed by calculating the excited state dipole moments (>23D). The reported synthetic method enables fine-tuning of the fluorescent properties for the developed photoactive molecular systems by varying donor fragments. The obtained compounds could be of particular interest in the design of photoactive organic and hybrid materials.

Volatile Solid‐Assisted Molecular Assembly Enables Eco‐Friendly Processed Organic Photovoltaic Cells with High Efficiency and Photostability

AbstractAchieving environmentally friendly solvent‐processed high‐performance organic photovoltaic cells (OPVs) is a crucial step toward their commercialization. Currently, OPVs with competitive efficiencies rely heavily on harmful halogenated solvent additives. Herein, the green and low‐cost 9‐fluorenone (9‐FL) is employed as a solid additive. By using the o‐xylene/9‐FL solvent system, the PM6:BTP‐eC9‐based devices deliver power‐conversion efficiencies of 18.6% and 17.9% via spin‐coating and blade‐coating respectively, outperforming all PM6:Y‐series binary devices with green solvents. It is found that the addition of 9‐FL can regulate the molecular assembly of both PM6 and BTP‐eC9 in film‐formation (molecule‐level mixing) and post‐annealing (thermal‐assisted molecular reorganization with additive volatilization) stages, so as to optimize the blend morphology. As a result, the charge transport ability of donor and acceptor phases are simultaneously enhanced, and the trap‐assisted recombination is reduced, which contributes to the higher short‐circuit current density and fill factor. Moreover, the generation of photo‐induced traps is significantly suppressed, resulting in improved stability under illumination. It is further demonstrated the excellent universality of 9‐FL in various photoactive systems, making it a promising strategy to advance the development of eco‐friendly OPVs.

Exploiting the photophysical features of DMAN template in ITQ-51 zeotype in the search for FRET energy transfer.

The combination between photoactive molecules and inorganic structures is of great interest for the development of advanced materials in the field of optics. Particularly, zeotypes with extra-large pore size are attractive because they allow the encapsulation of bulky dyes. The microporous aluminophoshate Mg-ITQ-51 (IFO-type structure) represents an ideal candidate because of the synergic combination of two crucial features: the IFO framework itself, which is composed of non-interconnected one-dimensional extra-large elliptical channels with a diameter up to 11 Å able to host bulky guest species, and the particular organic structure-directing agent used for the synthesis (1,8-bis(dimethylamino)naphthalene, DMAN), which efficiently fills the IFO pores, and is itself a photoactive molecule with interesting fluorescence properties in the blue range of the visible spectrum, thus providing a densely-incorporated donor species for FRET processes. Besides, occlusion of DMAN dye in the framework triggers a notable improvement of its fluorescence properties by confinement effect. To extend the action of the material and to mimic processes such as photosynthesis in which FRET is essential, two robust laser dyes with bulky size, rhodamine 123 and Nile Blue, have been encapsulated for the first time in a zeolitic framework, together with DMAN, in a straightforward one-pot synthesis. Thus, photoactive systems with emission in the entire visible range have been achieved due to a partial FRET between organic chromophores protected in a rigid aluminophosphate matrix.

Photoinduced Electron Transfer in Inclusion Complexes of Carbon Nanohoops.

ConspectusPhotoinduced electron transfer (PET) in carbon materials is a process of great importance in light energy conversion. Carbon materials, such as fullerenes, graphene flakes, carbon nanotubes, and cycloparaphenylenes (CPPs), have unusual electronic properties that make them interesting objects for PET research. These materials can be used as electron-hole transport layers, electrode materials, or passivation additives in photovoltaic devices. Moreover, their appropriate combination opens up new possibilities for constructing photoactive supramolecular systems with efficient charge transfer between the donor and acceptor parts. CPPs build a class of molecules consisting of para-linked phenylene rings. CPPs and their numerous derivatives are appealing building blocks in supramolecular chemistry, acting as suitable concave receptors with strong host-guest interactions for the convex surfaces of fullerenes. Efficient PET in donor-acceptor systems can be observed when charge separation occurs faster than charge recombination. This Account focuses on selected inclusion complexes of carbon nanohoops studied by our group. We modeled charge separation and charge recombination in both previously synthesized and computationally designed complexes to identify how various modifications of host and guest molecules affect the PET efficiency in these systems. A consistent computational protocol we used includes a time-dependent density-functional theory (TD-DFT) formalism with the Tamm-Dancoff approximation (TDA) and CAM-B3LYP functional to carry out excited state calculations and the nonadiabatic electron transfer theory to estimate electron-transfer rates. We show how the photophysical properties of carbon nanohoops can be modified by incorporating additional π-conjugated fragments and antiaromatic units, multiple fluorine substitutions, and extending the overall π-electron system. Incorporating π-conjugated groups or linkers is accompanied by the appearance of new charge transfer states. Perfluorination of the nanohoops radically changes their role in charge separation from an electron donor to an electron acceptor. Vacancy defects in π-extended nanohoops are shown to hinder PET between host and guest molecules, while large fully conjugated π-systems improve the electron-donor properties of nanohoops. We also highlight the role of antiaromatic structural units in tuning the electronic properties of nanohoops. Depending on the aromaticity degree of monomeric units in nanohoops, the direction of electron transfer in their complexes with C60 fullerene can be altered. Nanohoops with aromatic units usually act as electron donors, while those with antiaromatic monomers serve as electron acceptors. Finally, we discuss why charged fullerenes are better electron acceptors than neutral C60 and how the charge location allows for the design of more efficient donor-acceptor systems with an unusual hypsochromic shift of the charge transfer band in polar solvents.

Photoactive materials and devices for energy-efficient soft wearable optoelectronic systems

Advances in conventional inorganic photoactive materials, such as silicon and III–V compound semiconductors, enabled the development of high-performance and energy-efficient optoelectronic devices (e.g., photodetectors (PDs), light-emitting devices (LEDs), and photovoltaics (PVs)). These devices have recently been considered as essential components for multifunctional wearables that are capable of either providing a long-term stable power supply or visualizing various healthcare indicators in real time. Despite such progress, their rigid and bulky properties pose undesired challenges associated with low signal-to-noise ratios (SNRs) originating from a mechanical modulus mismatch between the skin and device, uncontrolled strain-induced crack propagation, and even long-term discomfort. As alternatives, emerging photoactive materials, such as atomically thin two-dimensional (2D) nanosheets and organic–inorganic halide perovskites with ultra-lightweight, ultrathin, and flexible characteristics have been significantly explored. These materials showed low-power multispectral sensing, effective light-matter coupling, and high compatibility to existing micro-/nano-fabrication technologies even on curved surfaces. Considering stretchability beyond flexibility, numerous research groups have employed well-established mechanical designs including a pre-strain-induced buckled structure with ultrathin layers, neutral-mechanical plane, and rigid-island array configuration with wavy interconnects. Recently, in addition to the above methodology, novel materials strategies regarding intrinsic stretchability and autonomous self-healability were introduced to improve the areal density and electrical/mechanical reliability through removal of serpentine interconnects, as well as adoption of tough damage-resistant polymers with efficient strain dissipation, low glass-transition temperature, and dynamically crosslinked bonds. In this light, the aforementioned methods would be essential to make current flexible photoactive devices intrinsically and durably stretchable. Here, we provide an overview of high-performance photovoltaic/photoemissive materials and devices and their applications to soft wearable energy-efficient optoelectronic systems. In particular, materials synthesis, device fabrication/assembly, and reconfigurable integration used in photoactive material-based wearable modular optoelectronic systems were timely described through a rigorous review of recent results.

Computational design and properties elucidation of new (FAPbI3)1−x-y(MAPbBr3)y(CsPbBr3)x photoactive systems for their application in perovskite solar cells

Computational design and properties elucidation of new (FAPbI3)1−x-y(MAPbBr3)y(CsPbBr3)x photoactive systems for their application in perovskite solar cells

Synthesis and comparative study of the structural and optical properties of binary ZnO-based composites for environmental applications.

The development of photoactive systems to solve serious environmental problems is a key objective of researchers and remains a real challenge. Herein, n-p heterojunction ZnO-based composites were developed to achieve better photocatalytic performance in methylene blue (MB) degradation under natural solar irradiation. The hydrothermal technique was used to synthesize zinc oxide (ZnO)/metal oxide (MO) composites, with a molar ratio of 1 : 1 (MO = Mn3O4; Fe3O4; CuO; NiO). Various characterization techniques were used for the analysis of the structural, morphological and optical properties. X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Spectroscopy (EDX) Diffuse Reflectance Spectroscopy analysis (DRS), and Diffuse Reflectance Spectroscopy analysis (DRS) validated the presence of two phases for each sample, excluding any impurities. Indeed, the ZnO structure was not affected by the coupling with MO, confirming that MO was well dispersed on the surface of the ZnO crystalline lattice for each composite. Eventually, the photocatalytic performance evaluation test of the synthesized photocatalysts was carried out on aqueous MB solution. According to the results, the ZnO/Fe3O4 nano-catalyst showed the best photodegradation efficiency. This result suggests that the formation of Fe3O4/ZnO as a p/n heterojunction reduces the recombination of photo-generated electron/hole pairs and broadens the solar spectral response range, resulting in significant photocatalytic efficiency. Meanwhile, the possible mechanism for degradation of the MB was discussed.

Synthesis and photobiological evaluation of Ru(II) complexes with expanded chelate polypyridyl ligands

Photoreactive Ru(II) complexes capable of ejecting ligands have been used extensively for photocaging applications and for the creation of “photocisplatin” reagents. The incorporation of distortion into the structure of the coordination complex lowers the energy of dissociative excited states, increasing the yield of the photosubstitution reaction. While steric clash between ligands induced by adding substituents at the coordinating face of the ligand has been extensively utilized, a lesser known, more subtle approach is to distort the coordination sphere by altering the chelate ring size. Here a systematic study was performed to alter metal-ligand bond lengths, angles, and to cause intraligand distortion by introducing a “linker” atom or group between two pyridine rings. The synthesis, photochemistry, and photobiology of five Ru(II) complexes containing CH2, NH, O, and S-linked dipyridine ligands was investigated. All systems where stable in the dark, and three of the five were photochemically active in buffer. While a clear periodic trend was not observed, this study lays the foundation for the creation of photoactive systems utilizing an alternative type of distortion to facilitate photosubstitution reactions.

Accelerated oxygen evolution kinetics on hematite by Zn2+ for boosting the photoelectrochemical water oxidation

The sluggish oxygen evolution reaction (OER) kinetics on hematite (α-Fe2O3) has constrained the photoelectrochemical (PEC) performance for water oxidation. Considering the regulatory effect of Zn for electrocatalytic OER, the Zn doped α-Fe2O3 nanowire is successfully prepared and served as the photoanode for PEC water oxidation. The results reveal the theoretical overpotential for the limiting step (from OH* to O*) is decreased by ca. 320 mV after Zn doing, which indicates an incredibly improved catalytic performance of OER. The Zn doped α-Fe2O3 displays PEC performance improvement over the bare α-Fe2O3, photocurrent density increases up to 0.88 mA/cm2(1.23 VRHE, 1 M NaOH), which shows a 44-fold increase than the α-Fe2O3. Meanwhile, the onset potential also shifts negatively by 300 mV, which also agrees well with the decreased OER overpotential. This work provides a deep understanding of the role of Zn in the α-Fe2O3 photoanodes and the strategy could be extended to other photoactive systems.

Synergistic interplay between photoisomerization and photoluminescence in a light-driven rotary molecular motor

Photoactuators and photoluminescent dyes utilize light to perform mechanical motion and undergo spontaneous radiation emission, respectively. Combining these two functionalities in a single molecule would benefit the construction of advanced molecular machines. Due to the possible detrimental interaction between the two light-dependent functional parts, the design of hybrid systems featuring both functions in parallel remains highly challenging. Here, we develop a light-driven rotary molecular motor with an efficient photoluminescent dye chemically attached to the motor, not compromising its motor function. This molecular system shows efficient rotary motion and bright photoluminescence, and these functions can be addressed by a proper choice of excitation wavelengths and solvents. The moderate interaction between the two parts generates synergistic effects, which are beneficial for lower-energy excitation and chirality transfer from the motor to the photoluminescent dye. Our results provide prospects towards photoactive multifunctional systems capable of carrying out molecular rotary motion and tracking its location in a complex environment.

Characterizing the excited states of large photoactive systems by exciton models

AbstractThe theoretical investigation of excited state for large photoactive systems plays the fundamental role in understanding various optical processes in material and biological system. Frenkel exciton (FE) model describing the excitation of the whole system as a collective effect of quasi‐particles of excitons, that is, bound electron–hole pairs, is well‐known as a simple but powerful theoretical scheme to present a clear and insightful physical picture for complicated excited state problems. In this mini‐review, we summarize our recent developments of quantum chemical methods based on exciton models and their related applications for large photoactive systems. It is shown that our developed ab initio renormalized exciton model (REM) and block interaction product state (BIPS) schemes provide new efficient and automatic low‐scaling excited state methods for both localized and delocalized excited states in large systems. Illustrative examples including simulations of both absorption and emission spectrum in large sized molecular aggregates, indicate the exciton model based methods provide promising computational tools for unravel the mechanism of photophysical and photochemical processes in large photoactive systems.