Near-Infrared Organic Small-Molecule Photosensitizer With O Self-Supply for Cancer Photodynamic-Photothermal Synergistic Therapy.

Tumor hypoxia and heat resistance as well as the light penetration deficiency severely compromise the phototherapeutic efficacy, developing phototherapeutic agents to overcome these issues has been sought-after goal. Herein, a diradical-featured organic small-molecule semiconductor, namely TTD-CN, has been designed to show low exciton binding energy of 42 meV by unique dimeric π-π aggregation, promoting near-infrared (NIR) absorption beyond 808 nm and effective photo-induced charge separation. More interestingly, its redox potentials are tactfully manipulated for water splitting to produce O and reduction of O to generate O .

Real-time spectroscopic tracking of efficient intersystem crossing triggered by the heavy-atom effect in di-heteroatomic organic phosphorescent molecules.

The development of efficient and long-lived halogen-free organic phosphorescent molecules remains a challenge. For the single-heteroatomic 9,10-dihydroacridine (AcH), the evolution of singlet and triplet excited state absorption signals reveals an intersystem crossing (ISC) lifetime of 8.2 ns and a triplet state lifetime of 0.

Effective promotion of steric hindrance effect on singlet-triplet transition of para-linked carbazole-biphenyl by transient absorption spectroscopy.

The para-linked carbazole-biphenyl (CBP) is commonly utilized in phosphorescent organic light-emitting diodes. This study investigates the steric hindrance and heavy-atom effects in CBP derivatives through transient absorption spectroscopy. In contrast to CBP, CBP derivatives shows new triplet-triplet absorption signals and isosbestic points, accompanied by the decay of excited state absorption signal, which indicates the occurrence of intersystem crossing (ISC).

Carrier transfer in quasi-2D perovskite/MoS monolayer heterostructure.

Two-dimensional layered semiconductors have attracted intense interest in recent years. The van der Waals coupling between the layers tolerates stacking various materials and establishing heterostructures with new characteristics for a wide range of optoelectronic applications. The interlayer exciton dynamics at the interface within the heterostructure are vitally important for the performance of the photodetector and photovoltaic device.

Managing Edge States in Reduced-Dimensional Perovskites for Highly Efficient Deep-Blue LEDs.

Pure-halide reduced-dimensional perovskites, featuring large exciton binding energy and tunable bandgap, show great potential for high-efficiency deep-blue perovskite light-emitting diodes (PeLEDs). However, their efficiency, particularly in the low n-value phase domain ("n" represents the number of octahedral sheets), lags behind analogous perovskite emitters. Herein, it is demonstrated that the vibration of edge-dangling octahedra in the low n-value phase activates notorious exciton-phonon (EP) coupling, thereby deteriorating efficiency.

Ultrafast energy transfer dynamics in CsPbBr nanoplatelets-BODIPY heterostructure.

Understanding and directing the energy transfer in nanocrystals-chromophore heterostructure is critical to improve the efficiency of their photocatalytic and optoelectronic applications. In this work, we studied the energy transfer process between inorganic-organic molecular complexes composed of cesium halide perovskite nanoplatelets (CsPbBr NPLs) and boron dipyrromethene (BODIPY) by photoluminescence spectroscopy (PL), time-correlated single photon-counting (TCSPC) and femtosecond transient absorption spectroscopy. The quenching of PL in CsPbBr NPLs occurred simultaneously with the PL enhancement of BODIPY implied the singlet energy transfer process.

Stimulating Phonon Bottleneck Effect in Organic Semiconductors by Charge-Transfer-Mediated J-Aggregation.

Hot carriers rapidly lose kinetic energies on a subpicosecond time scale, posing significant limitations on semiconductors' photon-conversion efficiencies. To slow the hot carrier cooling, the phonon bottleneck effect is constructed prevalently in quantum-confined structures with discrete energy levels. However, the maximum energy separation (Δ) between the energy levels is in a range of several hundred meV, leading to unsatisfactory cooling time.

Eliminating Halogen Vacancies Enables Efficient MACL-Assisted Formamidine Perovskite Solar Cells.

Methylammonium chloride (MACl) additive is almost irreplaceable in high-performance formamidine perovskite photovoltaics. Nevertheless, Some of the problems that can arise from adding MACl are rarely mentioned. Herein, it is proposed for the first time that the addition of MACl would cause the non-stoichiometric ratio in the perovskite film, resulting in the halogen vacancy.

The interface microenvironment mediates the emission of a semiconductor nanocluster surface-dopant-involving direct charge transfer.

The interface microenvironment of doped quantum dots (QDs) is crucial in optimizing the properties associated with the photogenerated excitons. However, the imprecision of QDs' surface structures and compositions impedes a thorough understanding of the modulation mechanism caused by the complex interface microenvironment, particularly distinguishing the contribution of surface dopants from inner ones. Herein, we investigated interface-mediated emission using a unique model of an atomically precise chalcogenide semiconductor nanocluster containing uniform near-surface Mn dopants.

Asymmetric Π-Bridge Engineering Enables High-Permittivity Benzo[1,2-B:4,5-b']Difuran-Conjugated Polymer for Efficient Organic Solar Cells.

Organic solar cells (OSCs) exhibit complex charge dynamics, which are closely correlated with the dielectric constant (ɛ ) of photovoltaic materials. In this work, a series of novel conjugated copolymers based on benzo[1,2-b:4,5-b']difuran (BDF) and benzotriazole (BTz) is designed and synthesized, which differ by the nature of π-bridge from one another. The PBDF-TF-BTz with asymmetric furan and thiophene π-bridge demonstrates a larger ɛ of 4.

Realizing Photocatalytic Overall Water Splitting by Modulating the Thickness-Induced Reaction Energy Barrier of Fluorenone-Based Covalent Organic Frameworks.

Direct photocatalytic hydrogen and oxygen evolution from water splitting is an attractive approach for producing chemical fuels. In this work, a novel fluorenone-based covalent organic framework (COF-SCAU-2) is successfully exfoliated into ultrathin three-layer nanosheets (UCOF-SCAU-2) for photocatalytic overall water splitting (OWS) under visible light. The ultrathin structures of UCOF-SCAU-2 greatly enhance carrier separation, utilization efficiency, and the exposure of active surface sites.

Unraveling Size-Dependent Ion-Migration for Stable Mixed-Halide Perovskite Light-Emitting Diodes.

Mixed-halide perovskites show tunable emission wavelength across the visible-light range, with optimum control of the light color. However, color stability remains limited due to the notorious halide segregation under illumination or an electric field. Here, a versatile path toward high-quality mixed-halide perovskites with high emission properties and resistance to halide segregation is presented.

Enhanced Performance of CsPbIBr Perovskite Solar Cell by Modified Zinc Oxide Nanorods Array with [6,6]-Phenyl C Butyric Acid.

Although Metal oxide ZnO is widely used as electron transport layers in all-inorganic PSCs due to high electron mobility, high transmittance, and simple preparation processing, the surface defects of ZnO suppress the quality of perovskite film and inhibit the solar cells' performance. In this work, [6,6]-Phenyl C butyric acid (PCBA) modified zinc oxide nanorods (ZnO NRs) is employed as electron transport layer in perovskite solar cells. The resulting perovskite film coated on the zinc oxide nanorods has better crystallinity and uniformity, facilitating charge carrier transportation, reducing recombination losses, and ultimately improving the cells' performance.

Design of BPEA-based derivatives with high singlet fission performance: a theoretical perspective.

The development of singlet fission (SF) is greatly hindered by the severe shortage of the types and numbers of SF materials. Here, essential energy conditions and SF-related competitive processes of a series of BPEA derivatives, which are a kind of new promising SF material, are investigated theoretically. Encouraging advantages and interesting laws of key energy conditions of those derivatives were found and potential BPEA derivatives were predicted.

Direct Observation of Ultrafast Relaxation Dynamics of a Mixed Excimer State in Perylene Monoimide Dimer by Femtosecond Transient Absorption.

A J-type dimer PMI-2, two perylene monoimides linked by butadiynylene bridger was prepared, and its excited-state dynamics was studied using ultrafast femtosecond transient absorption spectroscopy, along with steady-state spectroscopy and quantum chemical calculations. It is evidently demonstrated that the symmetry-breaking charge separation (SB-CS) process in PMI-2 is positively mediated by an excimer, which is mixed by localized Frenkel excitation (LE) and an interunit charge transfer (CT) state. Kinetic studies show that, with the polarity increasing of the solvent, the transformation of excimer from a mixture to the CT state (SB-CS) is accelerated, and the recombination time of the CT state is reduced obviously.

Observation of carrier transfer in a vertical 0D-CsPbBr/2D-MoS mixed-dimensional van der Waals heterojunction.

Two-dimensional transition metal dichalcogenides with outstanding properties open up a new way to develop optoelectronic devices such as phototransistors and light-emitting diodes. Heterostructure with light-harvesting materials can produce many photogenerated carriers via charge and/or energy transfer. In this paper, the ultrafast dynamics of charge transfer in zero-dimensional CsPbBr quantum dot/two-dimensional MoS van der Waals heterostructures are investigated through femtosecond time-resolved transient absorption spectroscopy.

Perylene Monoimide Phosphorus Salt Interfacial Modified Crystallization for Highly Efficient and Stable Perovskite Solar Cells.

Reducing the interfacial defects of perovskite films is key to improving the performance of perovskite solar cells (PSCs). In this study, two kinds of perylene monoimide (PMI) derivative phosphonium bromide salts were designed and used as a multifunctional interface-modified layer in PSCs. These two molecules are inserted between SnO and perovskite to produce a bidirectional passivation effect.

Synthesis-on-substrate of quantum dot solids.

Perovskite light-emitting diodes (PeLEDs) with an external quantum efficiency exceeding 20% have been achieved in both green and red wavelengths; however, the performance of blue-emitting PeLEDs lags behind. Ultrasmall CsPbBr quantum dots are promising candidates with which to realize efficient and stable blue PeLEDs, although it has proven challenging to synthesize a monodispersed population of ultrasmall CsPbBr quantum dots, and difficult to retain their solution-phase properties when casting into solid films. Here we report the direct synthesis-on-substrate of films of suitably coupled, monodispersed, ultrasmall perovskite QDs.

Broadband and strong visible-light-absorbing cuprous sensitizers for boosting photosynthesis.

Rational construction of broadband and strong visible-light-absorbing (BSVLA) earth-abundant complexes is of great importance for efficient and sustainable solar energy utilization. Herein, we explore a universal Cu(I) center to couple with multiple strong visible-light-absorbing antennas to break the energy level limitations of the current noble-metal complexes, resulting in the BSVLA nonprecious complex (). Systematic investigations demonstrate that double "ping-pong" energy-transfer processes in involving resonance energy transfer and Dexter mechanism enable a BSVLA between 430 and 620 nm and an antenna-localized long-lived triplet state for efficient intermolecular electron/energy transfer.

Transient Absorption Spectroscopy of a Carbazole-Based Room-Temperature Phosphorescent Molecule: Real-Time Monitoring of Singlet-Triplet Transitions.

Real-time monitoring of singlet-triplet transitions is an effective tool for studying room-temperature phosphorescent molecules. For femtosecond transient absorption (TA) spectroscopy of a 2,6-di(9-carbazol-9-yl) pyridine molecule in dimethyl sulfoxide (DMSO), the stimulated emission signal (380 nm) and the excited-state absorption signal (650 nm) reach their maximum intensity within 397 fs. Subsequently, the two signals decay with time and the triplet-triplet absorption (TTA) signal (400 nm) is enhanced synchronously, accompanied by an isosbestic point at 491 nm.

Carbon Nanodots with Nearly Unity Fluorescent Efficiency Realized via Localized Excitons.

Carbon nanodots (CDs) have emerged as an alternative option for traditional nanocrystals due to their excellent optical properties and low toxicity. Nevertheless, high emission efficiency is a long-lasting pursuit for CDs. Herein, CDs with near-unity emission efficiency are prepared via atomic condensation of doped pyrrolic nitrogen, which can highly localize the excited states thus lead to the formation of bound excitons and the symmetry break of the π-electron conjugation.

Synergistic Effects of Bipolar Additives on Grain Boundary-Mediated Charge Transport for Efficient Carbon-Based Inorganic Perovskite Solar Cells.

Carbon-based all-inorganic CsPbIBr perovskite solar cells offer high stability against heat and humidity and a suitable band gap for tandem and semitransparent photovoltaics. In CsPbIBr perovskite films, the defects at grain boundaries (GBs) cause charge trapping, reducing the efficiency of the cell. Electronic deactivation of GB has been a conventional strategy to suppress the trapping, but at the cost of charge carrier transport through the boundaries.