Reorganization Energy Research Articles

Understanding and Controlling the Formation of Nonradiative Defects in Blue Organic Triplet Emitters

Phosphorescent organic light-emitting devices (PHOLEDs) suffer from destructive molecular processes due to triplet-polaron and triplet-triplet annihilation. These processes are energetically driven and hence are particularly active in decreasing the lifetime of blue PHOLEDs. It has recently been shown that increasing triplet radiative rates via the Purcell effect effectively extends the device operational lifetime by reducing the triplet radiative lifetime, thus decreasing their density and the probability of triplet-annihilation reactions. We provide an analytical framework using Marcus theory to explain the observed, approximately exponential relationship between exciton energy and device lifetime. From transient drift-diffusion dynamics, we show that the Purcell effect reduces the exciton density in the steady state and increases the photoluminescent yield, thereby reducing defect generation rates and extending the device lifetime. We control the radiative rate of excitons in microcavities, thereby connecting the exciton energy and decay rates with the observed device lifetime. The device lifetime is shown to follow a power-law dependence on the Purcell factor (PFm) with m=1.5 to 2.5, dependent on the TTA-to-TPA ratio and photoluminescence quantum yield. From our analysis, a fivefold increase in PF has the potential to extend the blue PHOLED lifetime by up to 2 orders of magnitude, making the blue PHOLED lifetime comparable to that of state-of-the-art green PHOLEDs. Published by the American Physical Society 2024

Origins of Narrowband Emission in Nitrogen/Carbonyl Multiresonance Thermally Activated Delayed Fluorescence Emitters: Steric Locks and Vibrational Coupling Effects.

The incorporation of tert-butyl groups and spiro-functionalization into C═O/N-embedded multiresonance thermally activated delayed fluorescence (MR-TADF) systems has yielded materials with superior narrowband emission and excellent color purity. To elucidate the mechanisms underlying the enhanced properties, we present a theoretical study of a series of fused nitrogen/carbonyl derivatives with narrower emission profiles. The key steric factors that contribute to narrowband emission were identified through energy decomposition analysis, induced by structural relaxation in states S0 and S1. Additionally, we achieved potential narrower-band and deep-blue emission by targeting the suppression of vibrational coupling effects. This work provides compelling evidence that a 1-tert-butyl substitution, acting as an end lock, offers minimal reorganization energy and optimal structural stability when combined with a fused lock. Furthermore, new compounds such as 1tBuCZQ and 1tBuDQAO have been identified as promising MR-TADF emitters, delivering ultranarrowband emission as high-quality organic light-emitting diodes.

A butterfly shape acceptor with rigid skeleton and unique assembly enables both efficient organic photovoltaics and high-speed organic photodetectors

Abstract It remains challenging to design efficient bifunctional semiconductor materials in organic photovoltaic and photodetector devices. Here, we report a butterfly-shaped molecule, named WD-6, which exhibits low energy disorder and small reorganization energy due to its enhanced molecular rigidity and unique assembly with strong intermolecular interaction. The binary photovoltaic device based on PM6:WD-6 achieved an efficiency of 18.41%. Notably, an efficiency of 19.42% was achieved for the ternary device based PM6:BTP-eC9:WD-6. Moreover, the photodetection device based on WD-6 demonstrated an ultrafast response speed (205 ns response time at λ of 820 nm) and a high cutoff frequency of -3 dB (2.45 MHz), surpassing the values of most commercial Si photodiodes. Based on these findings, we show-cased an application of the WD-6-based photodetection device in high-speed optical communication. These results offer valuable insights into the design of organic semiconductor materials capable of simultaneously exhibiting high photovoltaic and photo detective performance.

Role of cavity strong coupling on single electron transfer reaction rate at electrode-electrolyte interface.

The physicochemical properties of molecules can be modulated through polariton formation under strong electromagnetic confinement. Here, we discuss the possibility of exploiting this phenomenon to increase the electron transfer rate at an electrode-electrolyte interface. Electron transfer theory under strong electromagnetic confinement can be extended to the electrode-electrolyte interface, and single-electron transfer reactions can be simulated using Gerischer's theory. Although single electron transfer in free space is well described using Marcus theory, the vacuum electric field can facilitate an additional electron transfer pathway via virtual photon excitation under cavity strong coupling conditions. Therefore, this binary reaction pathway for single electron transfer can yield a quasi-two-particle electron transfer process. This quantum behavior can dominate when the mode volume is small and when there are a large number of molecules in the vacuum electric field. Exploitation of polaritons in single electron transfer reactions can lead to enhanced electrochemical energy conversion systems.

Structural, Solvent, and Temperature Effects on Protein Junction Conductance.

Cytochrome b562 is a small redox-active heme protein that has served as an important model system for understanding biological electron transfer processes. Here, we present a comprehensive theoretical study of electron transport mechanisms in protein-metal junctions incorporating cytochrome b562 using a multi-scale computational approach. Employing molecular dynamics (MD) simulations, we generated junction geometries for both vacuum-dried and solvated conditions, with the protein covalently bound to gold contacts in various configurations. Coherent tunneling, described by the Landauer-Buttiker formalism within the density functional theory (DFT) framework, is compared to the incoherent hopping charge transport mechanism captured by the semi-classical Marcus theory. The tunneling was identified as the dominant mechanism explaining the experimental data measured on the cytochrome b562 junctions, exhibiting exponential yet very shallow distance dependence. While the structural orientations and protein contacts with the electrodes influence the junction conductance significantly, the solvation effects are relatively small, affecting the electronic properties mostly via the adsorption arrangement. On the other hand, the considerable temperature dependence of the conductance was found strong only for hopping, while the tunneling current magnitudes remain practically unaffected and are a good indicator of the coherent mechanism in this case.

Microscopic Origin of Twist-Dependent Electron Transfer Rate in Bilayer Graphene.

Using molecular simulation and continuum dielectric theory, we consider how electrochemical kinetics are modulated by the twist angle in bilayer graphene electrodes. By establishing a connection between the twist angle and the screening length of charge carriers within the electrode, we investigate how tunable metallicity modifies the statistics of the electron transfer energy gap. Constant potential molecular simulations show that the activation free energy for electron transfer increases with screening length, leading to a non-monotonic dependence on the twist angle. The twist angle alters the density of states, tuning the number of thermally accessible channels for electron transfer and the reorganization energy by affecting the stability of the vertically excited state through attenuated image charge interactions. Understanding these effects allows us to express the Marcus rate of interfacial electron transfer as a function of the twist angle in a manner consistent with experimental observations.

Ultrasound-Assisted Remote Benzylic C(sp3)-H Alkylation of N-Fluoroamides with Enol Silanes.

We have developed an ultrasound-assisted remote benzylic C(sp3)-H alkylation of N-fluorobenzamides with enol silanes; a series of β-aryl substituted propiophenones was generated in good to high yields. This reaction represents a formal C(sp3)-C(sp3) coupling and features simplicity, high efficiency, and wide substrate scope in a multiple-step sequential process, which involves N-F homolysis, 1,5-hydrogen atom transfer, benzylic radical addition, oxidation by copper(II) salt, and removal of the trimethylsilyl group. Also, DFT theoretical calculations and Marcus theory were employed to consolidate the proposed reaction mechanism.

Multiple Resonance Quasi‐fluorescence from BN‐Doped Aromatic Compounds Modified with “Naphthalene” Units Approaches the BT.2020 Green Light Standard

AbstractDeveloping fluorophores that conform to the Broadcast Service Television 2020 (BT.2020) standard presents a formidable challenge. Here, we propose an innovative approach that integrates two and three‐boron/nitrogen (BN2)‐embedded [4]helicene subunits with naphthalene, resulting in the synthesis of two novel narrowband bright green quasi‐fluorescent emitters, NT‐2B and NT‐3B for ultra‐high‐definition displays. These emitters exhibit minimal reorganization energy and Huang–Rhys factor, emitting at 510 and 511 nm in dilute toluene solution with exceptionally narrow full width at half maximum values of 15 and 14 nm, respectively. Notably, NT‐2B demonstrates an impressive photoluminescence quantum yield of 92.5 %, rapid radiative decay rate, and slow non‐radiative decay rate. Owing to their narrowband emission characteristics and outstanding optoelectronic properties, corresponding OLEDs based on NT‐2B demonstrate a high external quantum efficiency of 30.6 %, with an FWHM value of 21.5 nm and a CIEy of 0.74, positioning it as one of the leading narrow‐band green emitters.

Improving Optoelectronic Properties of Acceptor–Donor–Acceptor‐Type Non‐Fullerene Acceptors Containing Extended Fused Ring Donor Units for Efficient Organic Semiconductors

Developing efficient small molecule‐based non‐fullerene acceptors (NFAs) has gained huge attention in fabricating high‐efficiency and stable organic solar cells (OSCs). Herein, we designed and characterized eight new NFAs for OSCs. To investigate the potential of these newly designed NFAs series (IBH1–IBH8) for OSCs, various advanced quantum chemical simulation approaches are used and compared with the synthetic reference molecule IBH–R. Due to the extended donor cores, the IBH1–IBH8 molecules possess strong intramolecular and intermolecular interactions, which helps improve the thin‐film surface crystallinity. Moreover, the designed IBH1–IBH8 molecules present improved UV–visible absorption, narrower bandgaps, lower excitation, and binding energies, and improved photovoltaic characteristics. Furthermore, the impact on the intrinsic properties such as transition density matrix, density of state, electrostatic potential, distribution of frontier molecular orbitals, and reorganizational energies of holes and electrons are estimated. Additionally, the charge‐transfer phenomenon by establishing a donor:acceptor blend (PTB7–Th:IBH4) is analyzed, their geometric analyses are studied, and a good charge‐shifting process is found at the donor:acceptor interface. With these results, we demonstrated the enhancements in the optoelectronic and photovoltaic characteristics of OSCs by performing a simple end‐capped modulation. Hence, these molecules are recommended for the development of efficient and cost‐effective OSCs.

Electrolyte Effects in Electrocatalytic Kinetics†

Comprehensive SummaryTuning electrolyte properties is a widely recognized strategy to enhance activity and selectivity in electrocatalysis, drawing increasing attention in this domain. Despite extensive experimental and theoretical studies, debates persist about how various electrolyte components influence electrocatalytic reactions. We offer a concise review focusing on current discussions, especially the contentious roles of cations. This article further examines how different factors affect the interfacial solvent structure, particularly the hydrogen‐bonding network, and delves into the microscopic kinetics of electron and proton‐coupled electron transfer. We also discuss the overarching influence of solvents from a kinetic modeling perspective, aiming to develop a robust correlation between electrolyte structure and reactivity. Lastly, we summarize ongoing research challenges and suggest potential directions for future studies on electrolyte effects in electrocatalysis. Key ScientistsIn 1956, Marcus theory was developed to describe the mechanism of outer‐sphere electron transfer (OS‐ET). In 1992, Nocera et al. directly measured proton‐coupled electron transfer (PCET) kinetics for the first time, and their subsequent research in 1995 investigated the effects of proton motion on electron transfer (ET) kinetics. In 1999 and 2000, Hammes‐schiffer et al. developed the multistate continuum theory for multiple charge reactions and deduced the rate expressions for nonadiabatic PCET reactions in solution, laying the theoretical foundation for the analysis of PCET kinetics in electrochemical processes. In 2006, Saveant et al. verified the concerted proton and electron transfer (CPET) mechanism in the oxidation of phenols coupled with intramolecular amine‐driven proton transfer (PT). Their subsequent work in 2008 reported the pH‐dependent pathways of electrochemical oxidation of phenols.Electrolyte effects in electrocatalysis have gained emphasis in recent years. In 2009, Markovic's pioneering work proposed non‐covalent interactions between hydrated alkaline cations and adsorbed OH species in oxygen reduction reaction (ORR)/hydrogen oxidation reaction (HOR). In 2011, Markovic et al. significantly enhanced hydrogen evolution reaction (HER) activity in alkaline solution by improving water dissociation, which was assumed to dominate the sluggish HER kinetics in such media. In comparation, Yan et al. applied hydrogen binding energy (HBE) theory in 2015 to explain the pH‐dependent HER/HOR activity. Cations play a significant role in regulating the selectivity and activity of carbon dioxide reduction (CO2RR). In 2016 and 2017, Karen Chan et al. introduced the electric field generated by solvated cations to explain the cation effects on electrochemical CO2RR. Conversely, in 2021, Koper et al. suggested that short‐range electrostatic interactions between partially desolvated metal cations and CO2 stabilized CO2 and promoted CO2RR.Recent researches have combined the exploration of the electrical double layer (EDL) structure with theoretical analysis of PCET kinetics. In 2019, Huang et al. developed a microscopic Hamiltonian model to quantitatively understand the sluggish hydrogen electrocatalysis in alkaline media. In 2021, two meticulous studies from Shao‐Horn's group analyzed the effects of cations on reorganization energy and the impacts of hydrogen bonds between proton donors and acceptors on proton tunneling kinetics, respectively. Electrolyte effects on proton transport process were researched in recent years. In 2022, Hu et al. and Chen et al. proposed that the cation‐induced electric field distribution and pH‐dependent hydrogen bonding network connectivity played essential roles in proton transport, separately.

Machine learning assisted designing of hole-transporting materials for high performance perovskite solar cells

In recent years, the advancement of perovskite solar cells has accelerated, leading to continuous performance improvements. Over the past few years, machine learning (ML) has gained popularity among scientists researching perovskite solar cells. In this study, ML is used to screen hole-transporting materials for perovskite solar cells. To construct machine-learning (ML) models, data from prior investigations are collected. Out of four machine learning algorithms trained for predicting reorganization energy (Rh), the gradient boosting regression model stood out as the most effective, attaining an R2 value of 0.89. Data visualization analysis is then utilized to scrutinize the patterns within the dataset. 10,000 new compounds are generated. Chemical space of generated compounds is visualized using various measures. Minor structural modifications resulted in only a slight alteration in reorganization energy (Rh). The newly introduced multidimensional framework has the potential to efficiently screen materials in a short amount of time.

The Buddleja globosa (Matico) as natural Dye Sensitized Solar Cell: An experimental and theoretical studies based in TD-DFT/ periodic-DFT

The dye sensitizers coming from Buddleja Globosa, a Chilean regional flora, were analyzed and evaluated as a natural dye for the assembly of DSSC. The behavior toward the photoexcitation and electron injection steps was analyzed using time dependent functional theory (TD-DFT) and periodic (Periodic-DFT) calculations using a dye@(TiO2)48 model. The molecules analyzed present in the leaves were verbascoside, luteolin 7-O-glucoside, apigenin 7-O-glucoside, luteolin and gallic acid. The photoexcitation is driven by a π−π* transition localized in the frontier orbitals. These exhibit a ΔEHOMO−LUMO of approximately 4.0 eV which is very broad to facilitate an efficient photoexcitation process even though the LUMO density is localized in the acceptors group. In the adsorption and electron injection was found that the gallic acid and verbascoside facilitate a greater electron transport toward the metallic surface than the other dyes (ΔGinj = -1.52 and -1.03 eV, respectively). This was explained due to a low electron and hole reorganization energy in the gallic acid and verbacoside, respectively. Therefore, the greatest electron injection is originated due to a fast electron-hole transfer. Experimentally, a low overall conversion efficiency (η) was found. Thus, based in the computational discussion, this low efficiency is governed by the behaviour of the photoexcitation and not by the electron injection response.

The Hidden Mechanism: Excited-State Proton-Electron Pair Transfer in Metal Nanocluster Emission.

Comprehending the underlying factors that govern photoluminescence (PL) in metal nanoclusters (NCs) under physiological conditions remains a highly intriguing and unresolved challenge, particularly for their biomedical applications. In this study, we evaluate the critical role of excited-state proton-coupled electron transfer in the emission of metal NCs. Our findings demonstrate that hydronium ion (H3O+) binding can trigger a nonlinear, pH-dependent excited-state concerted electron proton transfer (CEPT) reaction. This involves simultaneous electron transfer from the Au(0) core to the Au(I)-ATT (ATT denotes 6-aza-2-thiothymidine) surface and proton transfer from H3O+ to the ATT ligand in a single step, greatly promoting vibrations and rotations of the Au(I)-ATT surface, resulting in substantial PL quenching of Au10(ATT)6 NCs. Further analyses show that the unique CEPT dynamics are strongly influenced by the opposing effects of increased reorganization energy and a larger pre-exponential factor on the electron transfer rate. Moreover, the proposed excited-state CEPT process is found to be prevalent in core-shell relaxation metal NCs, such as Au25(SR)18 (SR denotes thiolate) NCs, and serves as an important factor in limiting their PL emission. By simply controlling the pKa of the ligands, the emission performance of Au25(SR)18 can be easily regulated in physiological environments.

The Hidden Mechanism: Excited‐State Proton‐Electron Pair Transfer in Metal Nanocluster Emission

Comprehending the underlying factors that govern photoluminescence (PL) in metal nanoclusters (NCs) under physiological conditions remains a highly intriguing and unresolved challenge, particularly for their biomedical applications. In this study, we evaluate the critical role of excited‐state proton‐coupled electron transfer in the emission of metal NCs. Our findings demonstrate that hydronium ion (H3O+) binding can trigger a nonlinear, pH‐dependent excited‐state concerted electron proton transfer (CEPT) reaction. This involves simultaneous electron transfer from the Au(0) core to the Au(I)‐ATT (ATT denotes 6‐aza‐2‐thiothymidine) surface and proton transfer from H3O+ to the ATT ligand in a single step, greatly promoting vibrations and rotations of the Au(I)‐ATT surface, resulting in substantial PL quenching of Au10(ATT)6 NCs. Further analyses show that the unique CEPT dynamics are strongly influenced by the opposing effects of increased reorganization energy and a larger pre‐exponential factor on the electron transfer rate. Moreover, the proposed excited‐state CEPT process is found to be prevalent in core‐shell relaxation metal NCs, such as Au25(SR)18 (SR denotes thiolate) NCs, and serves as an important factor in limiting their PL emission. By simply controlling the pKa of the ligands, the emission performance of Au25(SR)18 can be easily regulated in physiological environments.

Elucidating the Advancement in the Optoelectronics Characteristics of Benzoselenadiazole-Based A2-D-A1-D-A2-Type Nonfullerene Acceptors for Efficient Organic Solar Cells.

The potential applications of nonfullerene acceptors (NFAs) such as tunable band gaps, improved charge separation, wide-range absorption, enhanced power conversion efficiency, and operational stability make them highly favorable for organic photovoltaic applications. Herein, we designed eight novel structurally modified nonfused benzoselenadiazole (BSe)-based A2-D-A1-D-A2-type NFAs for efficient organic solar cells (OSCs). These newly modeled BSe-based NFA series contain BSe as the central core. We employed strong electron-withdrawing moieties at terminal acceptor A2 to further enhance the optical, optoelectronics, and photovoltaic characteristics of OSCs. These designed molecules (HNM1-HNM8) along with the synthetic reference molecule (HNM) were thoroughly characterized by using efficient and advanced quantum chemical simulation approaches. Thus, to ascertain the enhancement of both optical and photochemical response, a thorough density functional theory (DFT) study was carried out using the M062X level in association with the 6-31G(d,p) basis set. All of the investigated molecules (HNM1-HNM8) had their excited states calculated using the time-dependent density functional theory method. The newly designed molecules (HNM1-HNM8) presented narrower band gaps, improved absorption and optoelectronics properties, and reduced excitation and binding energies. The electrostatic potential, density of states, transition density matrix, ionization potential, and electron affinity analysis of this newly designed (HNM1-HNM8) series revealed a strong coherence with those of the reference HNM molecule. Electron density difference mapping allowed us to visualize the spatial movement of electrons between the donor and acceptor molecules during excitation. This insight helps us to understand the efficiency of charge separation and recombination processes that are critical for the performance of organic photovoltaics. The reorganization energy and charge transfer analysis suggests that HNM1-HNM8 molecules could act as NFAs for organic photovoltaic applications to enhance their efficiency further. The donor: acceptor charge transfer analysis was also carried out, which revealed that the PTB7-Th:HNM2 donor:acceptor complex shows a great charge transportation process at the donor-acceptor interface. Moreover, the photovoltaic analysis shows that the designed (HNM1-HNM8) NFA series has a great potential to produce improved open-circuit voltage and fill factor values, which may be helpful in enhancing the overall PCEs of the OSCs.

Understanding the Nonradiative Charge Recombination in Organic Photovoltaics: From Molecule to Device

AbstractOrganic photovoltaics (OPVs) have made significant strides with efficiencies now exceeding 20%, positioning them as potential competitors to inorganic solar technologies. One of the most critical challenges toward this goal is the severe open‐circuit voltage (Voc) loss caused by the nonradiative charge recombination (NRCR). Herein, this review comprehensively summarizes the NRCR mechanisms and suppression techniques of OPVs across various scales from molecule to device. Specifically, the origins of NRCR in a single molecule are first summarized, and molecular design principles toward high photoluminescence quantum yield are reviewed following the Marcus theory. Next, the effect of aggregation on NRCR is reviewed, as well as the molecular and processing strategies to modulate the film packing for NRCR suppression. Furthermore, the progresses in the avoidance of nonradiative loss pathways mediated by charge transfer states and triplet states in donor:acceptor bulk heterojunctions are tracked. Besides, the interfacial optimization and device structure design to maximize the electroluminescent quantum efficiency are presented. Finally, several potential pathways toward curtailing NRCR for high‐performance OPVs are outlined. Therefore, this review shows an insightful perspective to understand and mitigate the NRCR at multi‐scales, and is poised to provide a clear roadmap for the next breakthrough of OPVs.

Investigating the acceptor tuned effect on INPOD-based efficient D-π-A organic chromophores for optoelectronic utilization through quantum chemical analysis

In this study, the dye-sensitized solar cells and non-linear optical capabilities of newly designed ((E)-2-amino-5-((5-(4-p-tolyl-1,2,3,3a, 4,8 b-hexahydrocyclopenta [b]indol-7-yl)thiophen-2-yl)methylene)thiazol-4(5H)-one (INPOD)-based A1-A6 organic chromophores were examined. To create a D-π-A structure, the A1-A6 molecules were positioned on the electron donor, spacer, and acceptor, respectively. The use of hybrid functionals including PBEPBE, CAM-B3LYP, and MPW1PW91 was evaluated for the maximum absorption wavelength of INPOD. According to the calculated outcomes, MPW1PW91 exhibited λmax closest to INPOD. Consequently, the optical absorption spectra of A1-A6 were employed by this method to identify the key factors. The photovoltaic characteristics of these compounds in dye-sensitized solar cells were studied theoretically. The acceptor category affected the photovoltaic performance of A1-A6. Through the quantum chemical technique in time-dependent density functional theory methods, the electronic charge distribution and intramolecular charge transfer inside the A1-A6 were found. Time-dependent density functional theory calculations revealed that all A1-A6 had a λmax, that was greater than the INPOD (437 nm) in the range of 564–806 nm. A6 demonstrated an electron reorganization energy of 0.2340 eV, while a hole reorganization energy of 0.1006 eV. These values represent the maximum mobility of holes and electrons among all values. Additionally, the open circuit voltage was calculated after coupling each compound with a PTB7-Th. By the Voc of 2.10, 2.06, 2.22, and 2.08 eV, the A1, A3, A4, and A5 dyes produced the best results, respectively. The A1-A6 sensitizers were used to derive the non-linear optical properties of the dipole moment, polarizability, and first-order hyperpolarizability. It was noticed from the calculated results that the A2 and A6 molecules have the best options for non-linear optical activity. It tested how well the A1-A6 dyes performed in terms of charge transfer, dye regeneration, electron injection driving force, light harvesting efficiency, transition density matrix, molecular electro-potential, and density of states. The computed result showed that A2 and A6 chromophores are excellent candidates for dye-sensitized solar cells. Finally, those dye derivatives would certainly work effectively as tuning-A in optoelectronic applications.

Role of Near-IR Sensitive Asymmetric A-DA′D–π–A-type Non-Fullerene Acceptors for Efficient Organic Solar Cells: A Theoretical Insight

Non-fullerene acceptor (NFA) molecules attracted huge attention from the photovoltaic community for their potential use in organic solar cells (OSCs). Herein, we designed a series of NFA materials (AR1–AR9) for OSCs by altering end-capped moieties. We employed various advanced density functional theory (DFT) and time-dependent (TD-DFT) approaches to characterize this designed AR1–AR9 series. Compared to the synthetic reference molecule ([Formula: see text], designed molecules AR1–AR9 revealed a smaller bandgap (1.85 eV), and improved absorption spectra ([Formula: see text] 741 nm) in comparison to [Formula: see text] ([Formula: see text] 668 nm), indicating the better potential for the tailored molecules. Furthermore, the designed series (AR1–AR9) shows lower reorganization energy values (for holes and electrons) and lower binding energies (0.323 eV), whereas, improved charge mobilities, showing them better candidates for OSCs. Moreover, frontier molecular orbitals (FMO), open-circuit voltages ([Formula: see text] and improved charge-transfer characteristics have also been investigated. These findings revealed that all developed NFAs exhibited a wide range of exciton dissociation constants and enhanced absorption efficiency with a relatively lower LUMO energy level. Therefore, we believe that these materials will be beneficial in boosting the power conversion efficiency (PCE) of OSC devices by improving their optoelectronic and photophysical properties.

Molecular Engineering of a Tumor-Targeting Thione-Derived Diketopyrrolopyrrole Photosensitizer to Attain NIR Excitation Over 850 nm for Efficient Dual Phototherapy.

Photosensitizers with near-infrared (NIR) excitation, especially above 800 nm which is highly desired for phototherapy, remain rare due to the fast nonradiative relaxation process induced by exciton-vibration coupling. Here, a diketopyrrolopyrrole-derived photosensitizer (DTPA-S) is developed via thionation of carbonyl groups within the diketopyrrolopyrrole skeleton, which results in a large bathochromic shift of 81 nm, endowing the photosensitizer with strong NIR absorption at 712 nm. DTPA-S is then introduced with a functional biomolecule (N3-PEG2000-RGD) via click reaction for the construction of integrin αvβ3 receptor-targeted nano-micelles (NanoDTPA-S/RGD), which endows the photosensitizer with a further superlarge absorption redshift of 138 nm, thus extending the absorption maxima to ≈850 nm. Remarkably, thiocarbonyl substitution increases the nonbonding characters in frontier molecular orbitals, which can effectively suppress the nonradiative vibrational relaxation process via reducing the reorganization energy, enabling efficient reactive oxygen species (ROS) generation under 880 nm excitation. Screened by in vitro and in vivo assays, NanoDTPA-S/RGD with high water solubility, excellent tumor-targeting ability, and photodynamic/photothermal therapy synergistic effect exhibits satisfactory phototherapeutic performance. Overall, this study demonstrates a new design of efficient NIR-triggered diketopyrrolopyrrole photosensitizer with facile installation of functional biomolecules for potential clinical applications.

Heterojunction Organic Solar Cells with Efficient Charge Mobility and Separation Capabilities Studied by DFT.

The properties of the active layer materials play a decisive role in determining the power conversion efficiency of organic solar cells (OSCs). Chlorophyll and its derivatives are abundant and environmentally friendly functional organic molecular materials. Using density functional theory (DFT) and time-dependent density functional theory (TD-DFT), we have calculated the absorption spectra and their excited state properties based on optimized ground state structures. It was found that bacteriochlorin exhibits superior structural properties, a smaller energy gap and hole reorganization energy, redshifted absorption spectra, and higher hole mobility compared to the donor D18. This suggests that bacteriochlorin exhibits superior donor properties. Comparative studies between o-AT-2Cl and m-AT-2Cl showed that o-AT-2Cl had superior acceptor properties, implying that differences in substitution positions can influence the physicochemical properties of non-fullerene acceptors (NFAs). Subsequently, six bulk heterojunctions (BHJs) were constructed by combining three donors with nonfused ring electron acceptors, o-AT-2Cl and m-AT-2Cl. The bacteriochlorin-based BHJs performed well among them, with BChl3/o-AT-2Cl and BChl4/o-AT-2Cl having the largest interfacial charge separation rate. The results suggested that BHJs composed of bacteriochlorin and NFAs can improve OSCs' photovoltaic performance, providing a feasible scheme for designing efficient OSCs.