Precision-Engineered Medium-Sized Molecular Host and Emitter for Ensuring Consistent Performance in Solution-Processed Narrowband OLEDs.

In this study, two novel multiple resonance (MR) emitters, DtCzBN and Cy-DtCzBN, were designed based on the well-known BCzBN structure and synthesized for narrowband solution-processed organic light-emitting diodes (OLEDs). Cy-DtCzBN possesses a dimeric V-shaped structure formed by coupling two individual DtCzBN units via a nonconjugated cyclohexane linker. When compared with DtCzBN, Cy-DtCzBN, as a medium-sized molecule, was found to maintain the optical and photophysical properties of the corresponding monomeric unit, DtCzBN, but exhibits high thermal stability, excellent solubility, and good film-forming ability. Additionally, solution-processed OLEDs were fabricated by using two sets of molecules: one set of small molecular hosts and emitters (i.e., mCP and DtCzBN) and the other set of medium-sized molecular hosts and emitters (i.e., Cy-mCP and Cy-DtCzBN). Notably, devices using medium-sized molecular hosts and emitters exhibited similar optical and photophysical properties but showed significantly improved reproducibility and thermal stability compared with those based on small molecular hosts and emitters. Our current study provides some insights into molecular design strategies for thermally stable hosts and emitters, which are highly suitable for solution-processed OLEDs.

Next-Generation Femtech: Urine-Based Cervical Cancer Diagnosis Using a Fluorescent Biothiol Probe with Controlled Smiles Rearrangement.

Cervical cancer screening is a crucial field of femtech (female technology). In this work, we disclosed a new femtech solution─a simple, straightforward, and on-site applicable urine-based cervical cancer diagnostic method using a fluorescent biothiol probe. Our newly developed nitrobenzene-based fluorescent probe, named NPS-B, effectively differentiates between cysteine and homocysteine within urine samples via controlled Smiles rearrangement. The analysis of emission-based signals offers the potential utility of this method in cervical cancer. NPS-B was designed by considering the substitution effect and structural polarity of the nitrobenzene-based fluorophore. This controlled modification of nitrobenzene-induced substantial intramolecular charge transfer changes in the fluorophore when exposed to biothiols, resulting in significant changes in photophysical properties. NPS-B displayed different emissions of cysteine and homocysteine in clinical human urine (without prior urine treatment). Overall, our findings provide insights not only into fundamental chemical science but also into the broader domain of applied sciences.

Novel π-Extended Indolocarbazole-Based Deep-Blue Fluorescent Emitter with Remarkably Narrow Bandwidth for Solution-Processed Organic Light-Emitting Diodes.

In solution-processed organic light-emitting diodes (OLEDs), achieving high color purity and efficiency is as important as that in vacuum processes. Emitters suitable for solution processing must have excellent solubility in organic solvents, high molecular weight, and compatibility with the host materials. In this study, we synthesized a deep-blue emitter that satisfies the above conditions by introducing a 1,4-bis(indolo[3,2,1-jk]carbazol-2-yl)benzene-based planar emitting core (DICz) structure and four 3,6-di-tert-butyl-9-phenyl-9H-carbazole (tCz) peripheral units, namely, 4tCz-DICz. A comparative compound, 4Hex-DICz, incorporating hexyl phenyl groups was synthesized. In contrast to 4Hex-DICz, 4tCz-DICz exhibited exceptional solubility in organic solvents and superior film-forming properties attributed to the presence of tCz units. Additionally, in the film state, the effective encapsulation of the emitting core (DICz) by the tCz units in 4tCz-DICz helps prevent undesirable molecular aggregation. The solution-processed OLEDs employing the CH-2D1 film, doped with 5 wt % 4tCz-DICz as the emitting layer, exhibited a deep-blue emission at 424 nm, characterized by a narrow bandwidth of 22 nm, and achieved a maximum external quantum efficiency (EQE) of approximately 4.0%. In contrast, the 4Hex-DICz-based device demonstrated an EQE of 2.91%. Consequently, we have successfully demonstrated that the introduction of four bulky tCz units into the DICz core is a promising molecular design strategy for the development of soluble indolocarbazole-based emitters, especially those used in high-performance deep-blue fluorescent OLEDs.

In Situ Activatable Nitrobenzene-Cysteine-Copper(II) Nano-complexes for Programmed Photodynamic Cancer Therapy.

Photodynamic therapy (PDT) has been used to reduce cancerous and precancerous cells via reactive oxygen species (ROS) generation from photosensitizers. Numerous photosensitizers are available today to treat a variety of diseases, but their therapeutic efficacy is hindered within the tumor microenvironment, and there are safety concerns associated with their non-specific activation. In this work, we disclosed a nano-therapeutic based on in situ activatable nitrobenzene-cysteine-copper(II) nano-complexes (NCCNs) that work within cancer cells. Among the NCCNs, CyP shows outstanding potential as a promising candidate for programmed photodynamic cancer therapy with its unique properties such as (i) bright near-infrared imaging, (ii) chemodynamic therapeutic effect, (iii) photodynamic therapeutic effect (types I and II), and (iv) anti-cancer effect by anti-angiogenesis in early cancer stage under light. Overall, this work opens up exciting possibilities for the development of innovative and effective treatments for cancer, paving the way for future advancements in the clinical medicine field.

Janus-Type ESIPT Chromophores with Distinctive Intramolecular Hydrogen-bonding Selectivity.

Excited-state intramolecular proton transfer (ESIPT)-based solid luminescent materials with multiple hydrogen bond acceptors (HBAs) remain unexplored. Herein, we introduced a family of Janus-type ESIPT chromophores featuring distinctive hydrogen bond (H-bond) selectivity between competitive HBAs in a single molecule. Our investigations showed that the central hydroxyl group preferentially forms intramolecular H-bonds with imines in imine-modified 2-hydroxyphenyl benzothiazole (HBT) chromophores but tethers the benzothiazole moiety in hydrazone-modified HBT chromophores. Imine-derived HBTs generally exhibit higher fluorescence efficiency, while hydrazone-derived HBTs show a reduced overlap between the absorption and fluorescence bands. Quantum chemical calculations unveiled the molecular origins of the biased intramolecular H-bonds and their impact on the ESIPT process. This Janus-type ESIPT chromophore skeleton provides new opportunities for the design of solid luminescent materials.

Perovskite Nanocrystals Protected by Hermetically Sealing for Highly Bright and Stable Deep-Blue Light-Emitting Diodes.

Metal-halide perovskite nanocrystals (NCs) have emerged as suitable light-emitting materials for light-emitting diodes (LEDs) and other practical applications. However, LEDs with perovskite NCs undergo environment-induced and ion-migration-induced structural degradation during operation; therefore, novel NC design concepts, such as hermetic sealing of the perovskite NCs, are required. Thus far, viable synthetic conditions to form a robust and hermetic semiconducting shell on perovskite NCs have been rarely reported for LED applications because of the difficulties in the delicate engineering of encapsulation techniques. Herein, a highly bright and durable deep-blue perovskite LED (PeLED) formed by hermetically sealing perovskite NCs with epitaxial ZnS shells is reported. This shell protects the perovskite NCs from the environment, facilitates charge injection/transport, and effectively suppresses interparticle ion migration during the LED operation, resulting in exceptional brightness (2916 cd m-2 ) at 451 nm and a high external quantum efficiency of 1.32%. Furthermore, even in the unencapsulated state, the LED shows a long operational lifetime (T50 ) of 1192 s (≈20 min) in the air. These results demonstrate that the epitaxial and hermetic encapsulation of perovskite NCs is a powerful strategy for fabricating high-performance deep-blue-emitting PeLEDs.

Rational Molecular Design Strategy for Host Materials in Thermally Activated Delayed Fluorescence-OLEDs Suitable for Solution Processing.

Herein, a novel core molecule for V-shaped host molecules was synthesized, wherein two carbazoles were directly linked to cyclohexane. Cy-mCP and Cy-mCBP hosts were also successfully prepared for solution-processable thermally activated delayed fluorescence organic light-emitting diodes (TADF-OLEDs). The Cy-mCP and Cy-mCBP molecules contained a cyclohexane linker directly linked to two small molecular hosts (mCP and mCBP), exhibiting twice the molecular weight while maintaining the basic properties of a single host molecule with improved film-forming ability and solubility in organic solvents. These host materials showed superior thermal stability and high glass transition temperatures compared to lower molecular weight hosts. Green TADF-OLEDs were prepared using the two host materials and 2,4,5,6-tetra(3,6-di-tert-butylcarbazol-9-yl)-1,3-dicyanobenzene (t4CzIPN) emitter, achieving device efficiencies similar to that of a low-molecular-weight host. However, after the incorporation of a V-shaped host, superior characteristics were observed in terms of the thermal stability and operational stability of the device. The synthesis of V-shaped molecules by directly linking two carbazoles to a cyclohexane linker is promising for the development of different hosts for solution-processable OLEDs.

Wavelength engineerable porous organic polymer photosensitizers with protonation triggered ROS generation.

Engineering excitation wavelength of photosensitizers (PSs) for enhanced reactive oxygen species (ROS) generation has inspired new windows for opportunities, enabling investigation of previously impracticable biomedical and photocatalytic applications. However, controlling the wavelength corresponding to operating conditions remains challenging while maintaining high ROS generation. To address this challenge, we implement a wavelength-engineerable imidazolium-based porous organic photocatalytic ROS generation system (KUP system) via a cost-effective one-pot reaction. Remarkably, the optimal wavelength for maximum performance can be tuned by modifying the linker, generating ROS despite the absence of metal ions and covalently attached heavy atoms. We demonstrate that protonated polymerization exclusively enables photosensitization and closely interacts with oxygen related to the efficiency of photosensitizing. Furthermore, superior tumor eradication and biocompatibility of the KUP system were confirmed through bioassays. Overall, the results document an unprecedented polymerization method capable of engineering wavelength, providing a potential basis for designing nanoscale photosensitizers in various ROS-utilizing applications.

Simplified Y6-Based Nonfullerene Acceptors: In-Depth Study on Molecular Structure-Property Relation, Molecular Dynamics Simulation, and Charge Dynamics.

Two new Y6 derivatives of symmetrical YBO-2O and asymmetrical YBO-FO nonfullerene acceptors (NFAs) are prepared with a simplified synthetic procedure by incorporating octyl and fluorine substituents onto the terminal 2-(3-oxo-2,3-dihydro-1H-inden-1-ylidene)malononitrile (INCN) moiety. By moving the alkyl substituents on the Y6 core to the terminal INCN moiety, the lowest unoccupied molecular orbital of the YBO NFAs increases without decreasing solubility, resulting in high open-circuit voltages of the devices. Molecular dynamics simulation shows that YBO-2O/-FO preferentially form core-core and terminal-terminal dimeric interactions, demonstrating their tighter packing structure and higher electron mobility than Y6, which is consistent with 2D grazing incidence X-ray scattering and space charge limited current measurements. In blend films, the hole transfer (HT) from YBO-2O/-FO to the polymer donor PM6 is studied in detail by transient absorption spectroscopy, demonstrating efficient HT from YBO-FO to PM6 with their suitable energy level alignment. Despite the simplified synthesis, YBO-FO demonstrates photovoltaic performance similar to that of Y6, exhibiting a power conversion efficiency of 15.01%. Overall, this design strategy not only simplifies the synthetic procedures but also adjusts the electrical properties by modifying the intermolecular packing and energy level alignment, suggesting a novel simplified molecular design of Y6 derivatives.

Reliable experimental method for determination of photoacidity revealed by quantum chemical calculations.

Photoacids are aromatic acids that exhibit significantly different acidities when they are electronically excited. Three experimental methods have been extensively used to determine the photoacidity, : fluorescence titration, the Förster cycle, and time-resolved experiments. However, the photoacidities determined by these experimental methods are not consistent. In this work, we used a theoretical method to evaluate the reliability of experimentally determined values. In particular, density functional theory (DFT) and time-dependent DFT calculations were used to obtain the changes in Gibbs free energy for acid dissociation reactions which are directly related to values. The Förster cycle, which is frequently used to experimentally determine the photoacidity due to its simplicity, yielded inconsistent results depending on how the transition energy was defined. We evaluated six empirical parameters extracted from the absorption and emission spectra of acidic and basic species of photoacids to adequately define the transition energy in the Förster cycle. And we found that the values obtained using the optical bandgap as the transition energy in the Förster cycle were in the best agreement with the results of quantum chemical calculations.

Sceptrin-Au nano-aggregates (SANA) for overcoming drug-resistant Gram-negative bacteria.

One of the recent advances in medical nanotechnology has been the development of nanoformulations to overcome drug-resistant bacterial infections. Herein, we disclose a new nano-antibiotic formulation based on sceptrin-Au nano-aggregates (SANA), which are drug-metal ion multiple complexes. Sceptrin is a natural compound from a marine organism (sponge) and was reported as a potential compound with drug activities. SANA consists of a sceptrin-Au ion and is a self-assembled nano-formation with electrostatic interaction. Interestingly, SANA showed superior antibiotic/antibiofilm activity toward carbapenem-resistant Gram-negative bacteria with low toxicity to red blood cells and endothelial cells. The working mechanism of SANA was identified with analysis of the extracellular reactive oxygen species level and membrane depolarization of bacteria. The feasibility of SANA as a new nano-antibiotic was demonstrated in CRPA-contaminated medical supplies where SANA inhibited the formation of biofilms as well as the growth of CRPA. This work presents a new concept for the development of next-generation nano-antibiotics and a more feasible clinical translational pathway.

Development of a fluorescent nanoprobe based on an amphiphilic single-benzene-based fluorophore for lipid droplet detection and its practical applications.

Lipid droplets (LDs) are crucial biological organelles connected with metabolic pathways in biological systems and diseases. To monitor the locations and accumulation of LDs in lipid-related diseases, the development of a visualization tool for LDs has gained importance. In particular, LD visualization using fluorescent probes has gained attention. Herein, a new fluorescent nanoprobe, BMeS-Ali, is developed that can sense LDs based on an amphiphilic single benzene-based fluorophore (SBBF). BMeS-Ali consists of hydrophilic (-NH2) and hydrophobic (-C12H25) moieties and exists as a micelle nanostructure in aqueous media. BMeS-Ali has a weak fluorescence, but its emission was dramatically enhanced upon exposure to the LD components such as oleic acids (OA) by reassembling its nano-formulation. BMeS-Ali showed a selective LD staining ability and great biocompatibility in cells (cancer cells and stem cells). It also showed a practical sensing ability towards biologically derived lipids and can be applied to the visualization of human fingerprints. We found that the nanoprobe BMeS-Ali has significant potential to serve as a practical dye and sensor for lipids, especially for LD imaging in the biomedical research area and broader industrial applications.

Beyond Woodward-Fieser Rules: Design Principles of Property-Oriented Chromophores Based on Explainable Deep Learning Optical Spectroscopy.

An adequate understanding of molecular structure-property relationships is important for developing new molecules with desired properties. Although deep learning optical spectroscopy (DLOS) has been successfully applied to predict the optical and photophysical properties of organic chromophores, how specific functional groups and solvents affect the optical properties is not clearly understood. Here, we employed an explainable DLOS method by applying the integrated gradients method to DLOS. The integrated gradients method allows us to obtain attributions, indicating how much the functional group contributes to the optical properties including the absorption wavelength and bandwidth, extinction coefficients, emission wavelength and bandwidth, photoluminescence quantum yield, and lifetime. The attributions of 54 functional groups and 9 solvent molecules to seven optical properties are quantified and can be used to estimate the optical properties of chromophores as in the Woodward-Fieser rule. Unlike the Woodward-Fieser rule for only the absorption wavelength, the attributions obtained in this work can be applied to estimate all seven optical properties, which makes a significant extension of the Woodward-Fieser rules. In addition, we demonstrated a strategy for utilizing the attributions in the design of molecules and in tuning the optical properties of the molecules. The design of molecular structures using attributions can revolutionize the development of optimal molecules.

Pyridine-NBD: A homocysteine-selective fluorescent probe for glioblastoma (GBM) diagnosis based on a blood test.

The precise in vitro diagnosis requires a high selectivity and sensitivity for a diagnostic agent. In this respect, fluorescent diagnostic probes have attracted attention in various clinical fields. Herein, we disclosed a tailor-made fluorescent homocysteine probe (NPO-Pyr) based on pyridine-thiol coordination and amine-addition. To date, Hcy has been recognized as an excellent biomarker for various diseases, but there still remain some limitations in detecting of Hcy due to its structural similarity to Cys. In this study, we developed a new fluorescent diagnostic probe for monitoring Hcy by incorporating 4-hydroxy-pyridine moiety into the skeleton of the NBD fluorophore. The incorporated pyridine moiety could coordinate with the thiol group at Hcy, followed by the amine-addition reaction (12 kJ/mol). Based on this rationale, NPO-Pyr responded to Hcy and exhibited turn-on properties with high selectivity and sensitivity (LOD: 0.084 ppm), and a fast-response time (<5 min). Furthermore, NPO-Pyr could predict the formation of glioblastoma (GBM) at an early stage through sensing Hcy in blood plasma (vs. healthy group, ∗∗∗∗P < 0.0001). Our findings have a significant importance across various fields from basic science to clinical translation, and we strongly believe that NPO-Pyr has the potential to fully replace the current complex GBM diagnostic process as a simpler in vitro agent.

Aryl-Annulated [3,2-a] Carbazole-Based Deep-Blue Soluble Emitters for High-Efficiency Solution-Processed Thermally Activated Delayed Fluorescence Organic Light-Emitting Diodes with CIEy <0.1.

In this study, we demonstrated two deep-blue TADF emitters, BO-tCzPhICz and BO-tCzDICz, for solution-processable thermally activated delayed fluorescence organic light-emitting diodes (TADF-OLEDs). They were synthesized by employing an organoboron acceptor and 9-(3,6-di-tert-butyl-9H-carbazol-9-yl)-5-phenyl-5,12-dihydroindolo[3,2-a]carbazole (tCzPhICz) and 12-(3,6-di-tert-butyl-9H-carbazol-9-yl)-15H-diindolo[2,3-b:1',2',3'-lm]carbazole (tCzDICz) as bulky aryl-annulated [3,2-a] carbazole donors, respectively. Both emitters showed sufficient solubility in organic solvents, narrow deep-blue emission, and small energy difference (ΔEST) between singlet and triplet states, which can be applied to solution-processable deep-blue TADF-OLEDs. Solution-processed OLEDs exploiting these TADF emitters displayed deep-blue electroluminescence with CIEy <0.1, and high external quantum efficiencies of 17.8 and 14.8% were observed for BO-tCzPhICz and BO-tCzDICz, respectively. The emitter bearing bulky ICz-based donating units shows highly promising potential for high-efficiency solution-processable deep-blue TADF-OLEDs.

Novel V-Shaped Bipolar Host Materials for Solution-Processed Thermally Activated Delayed Fluorescence OLEDs.

Three V-shaped host molecules with a cyclohexane linker were successfully synthesized for thermally activated delayed fluorescence organic light-emitting diodes (TADF-OLEDs). The unipolar host molecules, BBCzC and BTDC, contained two 9-phenyl-9H-3,9'-bicarbazole (PBCz) moieties and two 2,12-di-tert-butyl-7-phenyl-5,9-dioxa-13b-boranaphtho[3,2,1-de]anthracene (PDBNA) moieties, respectively. BCzTC, a bipolar host molecule, consisted of a donor unit, PBCz, and an acceptor unit, PDBNA, connected by a cyclohexane linker. Three host molecules showed good solubility in various organic solvents, making them suitable for solution processing. Among the solution-processed green TADF-OLEDs using three host molecules and a green TADF emitter, the one with BCzTC showed the highest external quantum efficiency of up to 30% with a high power efficiency of 71 lm W-1 and a current efficiency of 102 cd A-1. Compared with BBCzC and BTDC, BCzTC exhibited a relatively high photoluminescence quantum yield (PLQY), an excellent balance in hole and electron transport properties in the emitting layer, and more efficient energy transfer to the emitter, giving such an excellent device performance.

Deep Learning Optical Spectroscopy Based on Experimental Database: Potential Applications to Molecular Design.

Accurate and reliable prediction of the optical and photophysical properties of organic compounds is important in various research fields. Here, we developed deep learning (DL) optical spectroscopy using a DL model and experimental database to predict seven optical and photophysical properties of organic compounds, namely, the absorption peak position and bandwidth, extinction coefficient, emission peak position and bandwidth, photoluminescence quantum yield (PLQY), and emission lifetime. Our DL model included the chromophore-solvent interaction to account for the effect of local environments on the optical and photophysical properties of organic compounds and was trained using an experimental database of 30 094 chromophore/solvent combinations. Our DL optical spectroscopy made it possible to reliably and quickly predict the aforementioned properties of organic compounds in solution, gas phase, film, and powder with the root mean squared errors of 26.6 and 28.0 nm for absorption and emission peak positions, 603 and 532 cm-1 for absorption and emission bandwidths, and 0.209, 0.371, and 0.262 for the logarithm of the extinction coefficient, PLQY, and emission lifetime, respectively. Finally, we demonstrated how a blue emitter with desired optical and photophysical properties could be efficiently virtually screened and developed by DL optical spectroscopy. DL optical spectroscopy can be efficiently used for developing chromophores and fluorophores in various research areas.

Fullerene-Based Triads with Controlled Alkyl Spacer Length as Photoactive Materials for Single-Component Organic Solar Cells.

Two kinds of dumbbell-shaped acceptor-donor-acceptor (A-D-A)-type triad single-component (SC) photovoltaic molecules based on a benzodithiophene-rhodanine (BDTRh) core and [6,6]-phenyl-C61 butyric acid (PC61BA) termini, BDTRh-C2-PC61BA and BDTRh-C10-PC61BA, were synthesized by modulating the alkyl (C2 and C10) spacer lengths. Both SC photovoltaic structures had similar UV-vis spectra in solution, but BDTRh-C10-PC61BA showed a significantly higher absorption coefficient as a thin film. In films, a more facile intermolecular photo-induced charge transfer was observed for BDTRh-C10-PC61BA in the broad-band transient absorption measurements. BDTRh-C10-PC61BA also exhibited a higher hole mobility (by 25 times) and less bimolecular recombination than BDTRh-C2-PC61BA. By plotting the normalized external quantum efficiency data, a higher charge-transfer state was measured for BDTRh-C10-PC61BA, reducing its voltage loss. A higher power conversion efficiency of ∼2% was obtained for BDTRh-C10-PC61BA, showing higher open-circuit voltage, short-circuit current density, and fill factor than those of BDTRh-C2-PC61BA devices. The different carrier dynamics, voltage loss, and optical and photoelectrical characteristics depending on the spacer length were interpreted in terms of the film morphology. The longer decyl spacer in BDTRh-C10-PC61BA afforded a significantly enhanced intermolecular ordering of the p-type core compared to BDTRh-C2-PC61BA, suggesting that the alkyl spacer length plays a critical role in controlling the intermolecular packing interaction.

A Simple Route toward Next-Generation Thiobase-Based Photosensitizers for Cancer Theranostics.

Sulfur-substituted biocompatible carbonyl fluorophores have been recognized as effective heavy-atom-free photosensitizers (PSs) for cancer therapy due to their remarkable phototherapeutic properties. However, guidelines on their molecular design are still a substantial challenge. Most of the existing thiocarbonyl-based PSs are nonemissive in both the solution and restricted states, which hinders their further biomedical applications. Herein, we report the interesting finding that sulfur-substituted coumarins exhibit an uncommon phenomenon, aggregation-induced emission. More intriguingly, we also found that the introduction of a strong electron-accepting trifluoromethyl group is crucial to facilitate the mitochondrial-targeting ability of neutral coumarin fluorophores. The resulting CMS-2 PS displayed selective imaging of mitochondria and exhibited much higher photodynamic therapy efficiency toward cancer cells than that of the commercial PS erythrosine B. This work provides deep insight into the molecular design of heavy-atom-free thiobase-based PSs and simultaneously offers a great opportunity to develop novel mitochondrial-targeting fluorescent indicators with neutral bioinspired platforms.

Singlet Fission Dynamics of Colloidal Nanoparticles of a Perylenediimide Derivative in Solutions.

Singlet fission (SF) is an intriguing process in which a singlet exciton produces two triplet excitons in molecular aggregates. Perylenediimide (PDI) derivatives are promising materials for SF-based photovoltaics, and the SF process in PDI aggregates is important to investigate for their applications. In this work, we studied the entire SF process occurring in the colloidal nanoparticles of a PDI derivative in solutions by using time-resolved fluorescence and transient absorption (TA) experiments. PE-PDI was found to form the colloidal nanoparticles of H- and J-aggregates in polar solvents. The TA signals of PE-PDI aggregates in solutions were selectively measured by wavelength-dependent excitation. The TA signals were analyzed by using a global fitting analysis, and all kinetic parameters involved in the entire SF process were determined. Our current investigation has confirmed that fast SF occurs on the surface of the colloidal nanoparticles of PDI aggregates via the charge transfer mediated mechanism, giving a high quantum yield of triplet excitons.