Search

Two blends comprising new dicyanopyrazine‐based acceptors (m‐CN and p‐CN) and a carbazole‐based donor CPTBF are explored for exciplex formation. The CPTBF:m‐CN and CPTBF:p‐CN blends show the signature red‐shifted emission together with the delayed fluorescence observed in time‐resolved measurement, manifesting the characteristics of thermally activated delayed fluorescence (TADF). The electroluminescence (EL) device employing CPTBF:m‐CN (CPTBF:p‐CN) blend as the emitting layer (EML) achieved an EQE of 5.22% (2.05%) with the EL λmax centered at 607 nm (625 nm). The exciplex excitons can be efficiently extracted by a new benzobisthiadiazole‐based near‐infrared (NIR) emitter DCzPBBT, where a device is configured with CPTBF:m‐CN: (5 wt.%) DCzPBBT as the EML to achieve a high EQE of 5.32% and an EL λmax 758 nm. Further increase of the doping concentration to 10 wt.% of DCzPBBT exhibits a bathochromic shifted EL λmax to 772 nm with 94% spectral coverage in the NIR (>700 nm) region, while the device EQE retains at 4.06%. The superior device performance stems from the highly efficient energy transfer between the exciplex‐forming host and NIR dopant together. [ABSTRACT FROM AUTHOR]

Intrinsic strong coupling between excitons and anapole mode in self-hybridizing transition metal dichalcogenide (TMD) nanostructures has recently attracted much attention for their capability of improving exciton–anapole interactions as a consequence of the nonradiative feature of anapole mode and the excellent mode overlap in the self-hybridizing geometry. Here, we propose a strategy for further enhancing exciton–anapole coupling. By embedding Au dimers as plasmonic components in slotted bulk WS2 nanodisks, a plasmon-induced electric field strength enhancement over nearly 140 times is achieved compared to that of the bulk WS2 nanodisk, boosting the strong exciton–anapole hybridization with greatly enhanced Rabi splitting up to 532 meV. Importantly, we demonstrate not only the effect of the plasmon mode on the initial Rabi phase of the anapole mode but also the great reduction of the ultrafast energy transfer time by the constructed full-quantum model. The plasmon-assisted hybrid system proposed in this paper provides a promising approach for enhancing strong light–matter interactions and may pave the way for the development of high-performance TMD-based photonic devices. [ABSTRACT FROM AUTHOR]

The layer‐by‐layer (LbL) organic photovoltaics (OPVs) are constructed with wide‐bandgap donor PM1 and narrow‐bandgap acceptor L8‐BO. The exciton utilization near cathode is still challenging considering restricted diffusion distance of excitons and inability for transferring energy from L8‐BO to PM1. Herein, donor incorporation into acceptor layer (DIA) strategy is employed to improve exciton utilization near cathode. The efficiency of LbL OPVs can be improved from 18.02% to 18.81% by incorporating 10 wt% PM1 into L8‐BO layer, which is closely associated with efficient exciton separation into L8‐BO layer originated from more adequate donor/acceptor interface for faster charge transfer, as evidenced by magneto‐photocurrent and transient absorption results. The in situ test and morphological characterization clarify that molecular packing property can be improved benefited from prolonged aggregation and nucleation time of acceptor layer assisted by DIA strategy, contributing to more efficient charge transport and inhibited charge recombination in active layers. The thickness insensitive property of LbL OPVs can be also improved induced by DIA strategy, indicated by PCE retention value (82.2% vs. 74.0%) for PM1/L8‐BO:PM1 and PM1/L8‐BO OPVs when acceptor layer thickness increased to ≈180 nm. This work demonstrates the effectiveness of DIA strategy in improving efficiency and thickness tolerance of LbL OPVs. [ABSTRACT FROM AUTHOR]

The ongoing challenge in advancing organic light‐emitting diodes (OLEDs) is to mitigate performance degradation during operation, caused by the dissociation of molecular components and the ensuing defect formation. While defects can emerge throughout OLEDs with diverse detrimental effects, prior research has predominantly focused on those within the emission layer (EML), leaving other device areas unexplored. In this work, a previously overlooked, yet profound impact of defects in the hole transport layer (HTL) on charge and exciton dynamics in a phosphorescent OLED (PHOLED) is investigated. HTL defects confine and impede the injection of free holes into the EML, requiring an increased supply of electrons to maintain constant current in the device. Consequently, excitons become concentrated at the HTL/EML interface, leading to enhanced bimolecular annihilations and an 8% reduction in device efficiency. Furthermore, when HTL defects are within 8 nm from the interface, they can directly quench excitons, resulting in a substantial decrease in device efficiency by up to 76%. This defect‐induced exciton quenching occurs through both Dexter and Förster energy transfer, each with distinct distance dependence. The findings emphasize the necessity of preventing defect formation, particularly in proximity to the HTL/EML interface, to minimize efficiency degradation for PHOLEDs. [ABSTRACT FROM AUTHOR]

Multi-color fluorescent anti-counterfeiting technology possesses a wide range of application prospects. However, there is still a challenge on the development of new single-component multi-color fluorescent materials related to the excitation wavelength. Herein, we report an efficient multi-peak luminescent material, Sb3+, Mn2+ co-doped CsCdCl 3 , which emission with a long afterglow is related to the excitation wavelength. There are two independent energy transfer channels of Mn2+ under short- and long-wave excitation. Under 357 nm excitation, dual-emission is observed at 506 and 590 nm attributed to the 3P 1 –1S 0 and 4T 1 -6A 1 transitions of [SbCl 6 ]3- and Mn2+ ions, respectively. Under 254 nm excitation, the microcrystals have orange emission. Excitation wavelength-dependent and tunable dual-emission associated with the host self-captured excitons and [SbCl 6 ]3- to Mn2+ energy transfer. The microcrystal's afterglow time at room temperature is 3500 s, which is attributed to the modulation of the trap for Mn2+. These results indicate that the material has potential applications in the field of multicolor fluorescent anti-counterfeiting. [ABSTRACT FROM AUTHOR]

Organic ultra‐long room‐temperature phosphorescence (RTP) materials in the amorphous state have attracted widespread attention due to their simple preparation and flexibility to adopt various forms in sensors, bioimaging, and encryption applications. However, the amorphous molecular host for the host–guest RTP systems is highly demanded but limited. Here, a universal molecular host (DPOBP−Br) has been designed by integration of an amorphous moiety of diphenylphosphine oxide (DPO) and an intersystem crossing (ISC) group of 4‐bromo‐benzophenone (BP−Br). Various commercial fluorescence dyes were doped into the tight and transparent DPOBP−Br film, respectively, resulting in amorphous host–guest systems with ultra‐long RTP colors from green to red. It was found that DPOBP−Br acted as a universal "triplet exciton pump" for promoting the generation of triplet excitons in the guest, through energy transfer processes and external heavy‐atom effect based on DPOBP−Br. Interestingly, dynamic RTP was achieved by controlling residual oxygen concentration in the amorphous matrix by UV irradiation. Therefore, multi‐dimensional anti‐counterfeiting coatings were realized even on curved surfaces, simultaneously exhibiting spatial and 2D‐time dependence. This work provides a strategy to design new amorphous molecular hosts for RTP systems and demonstrates the advanced information encryption with tempo‐spatial resolution based on the dynamic ultra‐long RTP of an amorphous system. [ABSTRACT FROM AUTHOR]

Organic ultra‐long room‐temperature phosphorescence (RTP) materials in the amorphous state have attracted widespread attention due to their simple preparation and flexibility to adopt various forms in sensors, bioimaging, and encryption applications. However, the amorphous molecular host for the host–guest RTP systems is highly demanded but limited. Here, a universal molecular host (DPOBP−Br) has been designed by integration of an amorphous moiety of diphenylphosphine oxide (DPO) and an intersystem crossing (ISC) group of 4‐bromo‐benzophenone (BP−Br). Various commercial fluorescence dyes were doped into the tight and transparent DPOBP−Br film, respectively, resulting in amorphous host–guest systems with ultra‐long RTP colors from green to red. It was found that DPOBP−Br acted as a universal "triplet exciton pump" for promoting the generation of triplet excitons in the guest, through energy transfer processes and external heavy‐atom effect based on DPOBP−Br. Interestingly, dynamic RTP was achieved by controlling residual oxygen concentration in the amorphous matrix by UV irradiation. Therefore, multi‐dimensional anti‐counterfeiting coatings were realized even on curved surfaces, simultaneously exhibiting spatial and 2D‐time dependence. This work provides a strategy to design new amorphous molecular hosts for RTP systems and demonstrates the advanced information encryption with tempo‐spatial resolution based on the dynamic ultra‐long RTP of an amorphous system. [ABSTRACT FROM AUTHOR]

The presence of surface trap states (STSs) is one of the key factors to affect the electronic and optical properties of quantum dots (QDs), however, the exact mechanism of how STSs influence QDs remains unclear. Herein, we demonstrated the impact of STSs on electron transfer in CdSe QDs and triplet-triplet energy transfer (TTET) from CdSe to surface acceptor using femtosecond transient absorption spectroscopy. Three types of colloidal CdSe QDs, each containing various degrees of STSs as evidenced by photoluminescence and X-ray photoelectron spectroscopy, were employed. Time-resolved emission and transient absorption spectra revealed that STSs can suppress band-edge emission effectively, resulting in a remarkable decrease in the lifetime of photoelectrons in QDs from 17.1 ns to 4.9 ns. Moreover, the investigation of TTET process revealed that STSs can suppress the generation of triplet exciton and effectively inhibit band-edge emission, leading to a significant decrease in TTET from CdSe QDs to the surface acceptor. This work presented evidence for STSs influence in shaping the optoelectronic properties of QDs, making it a valuable point of reference for understanding and manipulating STSs in diverse QDs-based optoelectronic applications involving electron and energy transfer. [ABSTRACT FROM AUTHOR]

The strong coupling between electronic transitions and resonant cavity modes, facilitated by coherent energy transfer, presents unprecedented opportunities for tailoring the photoelectronic properties of constituent components. Here, the concept of Kerker effect is leveraged to demonstrate the dynamic control of scattering directionality in dielectric nanostructures by tuning the exciton‐photon coupling. First, theoretical evidence for a significant modification of the scattering directionality of a dielectric metastructure engineered by excitonic polaritons is provided. As a proof of concept, self‐coupled metasurfaces composed of bulk MoS2, which exhibit a forward/backward scattering ratio up to 20, are constructed. Importantly, tunable directionality is achieved by thermally controlling the excitonic coupling to the Mie modes. The simulated results are in good agreement with the experimental measurements, and the subsequent multipole decompositions effectively elucidate the underlying mechanism, attributed to the interplay between electric and magnetic dipole modes that are modified by excitons. The findings shed light on the control of light flow in the far field through coherent light–matter interactions, thereby opening up numerous possibilities for active optical antennas and quantum emitters on a nanoscale. [ABSTRACT FROM AUTHOR]

Zero-dimensional organic-inorganic hybrid metal halides that can realize single-component white emission have attracted extensive attention due to the high-quality requirements of solid-state lighting technology. Although efficient white emission can be obtained in metal halides, the realization of tunable emission and high color rendering index of single-component white light remains a challenge. Herein, we report the binary halide (TEA) 2 (MnCl 4) 1- x (SbCl 5) x (TEA+ = tetraethylammonium, C 8 H 20 N+), realizing warm white emission with a photoluminescence quantum yield of 86.24 %. (TEA) 2 (MnCl 4) 1- x (SbCl 5) x halides with multiple optical polyhedral units ([SbCl 5 ]2- pyramid and [MnCl 4 ]2- tetrahedron) shows triple-peaked emission at 460 nm (free excitons emission), 520 nm (d – d transitions of Mn2+ ions), and 630 nm (self-trapped excitons emission). Interestingly, (TEA) 2 (MnCl 4) 1- x (SbCl 5) x halides exhibit emission color tunability by changing excitation energy and temperature, respectively. A comparison of lifetime spectra, as well as the temperature-variation spectra, was utilized to elucidate the energy transfer mechanism between Sb3+ and Mn2+ ions. The single-component white light-emitting diode fabricated by (TEA) 2 (MnCl 4) 0.92 (SbCl 5) 0.08 sample exhibits a high color rendering index of 92. This approach involving multiple emission mechanisms from different polyhedrons represents a promising avenue for designing single-component white-light emitters. • (TEA) 2 (MnCl 4) 1- x (SbCl 5) x halides showed high-performance white light emission (PLQY∼86.24 %). • The relationship between the host and guest has been established. • The unique energy transfer occurs from Sb3+ ions to Mn2+ ions has been confirmed. • High-efficiency luminescence (CRI∼92, CCT∼4253 K) of the fabricated WLED can be applied in the lighting field. [ABSTRACT FROM AUTHOR]

[Display omitted] • Bi-bridge BiPO 4 /CdS heterojunction (BiPO 4 /Bi/CdS) with oxygen vacancy was fabricated. • BiPO 4 /Bi/CdS displayed high intersystem crossing efficiency. • The effective intersystem crossing from singlet to triplet excitons facilitated 1O 2 production. • BiPO 4 /Bi/CdS exhibits excellent photocatalytic activity in ofloxacin degradation. • Mechanism of type-II heterojunction based on exciton energy transfer was first set forth. The separation of photogenerated charge carriers has been widely investigated, but exciton effects in type-II heterojunctions are often overlooked. Herein, the Bi-bridge BiPO 4 /CdS type-II heterojunction (BiPO 4 /Bi/CdS) with oxygen vacancy was successfully fabricated. BiPO 4 /Bi/CdS displayed stronger phosphorescence emission than BiPO 4 /Bi, suggesting the higher efficiency of intersystem crossing. The effective intersystem crossing from singlet to triplet excitons facilitated the activation of O 2 to singlet oxygen (1O 2), which was the product of energy transfer from the triplet excitons to the ground-state O 2 molecule. The synergies between oxygen vacancy, surface plasmon resonance of Bi and heterojunction-construction promoted charge carrier separation and the generation of 1O 2. As a result, BiPO 4 /Bi/CdS exhibited excellent photocatalytic activity in ofloxacin degradation with 93% degradation efficiency and 55% mineralization efficiency under the joint action of 1O 2 and h+ as reactive species. More importantly, the mechanism of BiPO 4 /Bi/CdS type-II heterojunction was set forth from the coupling of charge carriers and exciton effects. This work sheds new light on the regulation of excitonic effects in type-II heterojunction and provides unique insight into 1O 2 production. [ABSTRACT FROM AUTHOR]

• A series of Mn-doped A 2 PbBr 4 2D perovskites are synthesized and the luminescence properties of Mn2+ ions in related to the A-site cations is explored. • The highest efficiency of the energy transfer from excitons to Mn2+ reaches as high as 78.08 % in (PPA) 2 PbBr 4 :60 % Mn2+ 2D perovskite. • The luminescence mechanism of Mn-doped (PPA) 2 PbBr 4 perovskite with different Mn2+ concentrations are investigated by temperature dependent PL spectra. The incorporation of Mn2+ ions has been widely used to modulate optical properties of two-dimensional (2D) organic-inorganic hybrid perovskites (OIHPs). However, the luminescence mechanism of Mn2+ ions that is related to the A-site cations remains largely unexplored. Herein, we report the synthesis of a series of Mn-doped A 2 PbBr 4 (A = C 6 H 5 (CH 2) n NH 3 , n = 1,2,3,4,) 2D perovskites. The (C 6 H 5 (CH 2) 3 NH 3) 2 PbBr 4 ((PPA) 2 PbBr 4) 2D perovskite exhibited a maximum photoluminescence (PL) quantum yield of 67 %, a prolonged PL lifetime of 0.75 ms, and the highest energy transfer efficiency of 78.07 %. Furthermore, we systematically investigated the luminescence properties of Mn-doped (PPA) 2 PbBr 4 perovskite with different Mn2+ concentrations. The temperature dependent PL spectra indicate a thermalized de-trap process of self-trapped exciton at high temperatures and the presence of permanently shallow defect states in highly doped samples with lower activation energy. We reported the luminescence properties of Mn-doped 2D organic-inorganic hybrid perovskites, with a particular focus on the (PPA) 2 PbBr 4 perovskite material. [Display omitted] [ABSTRACT FROM AUTHOR]

Ce+3 doped CsLaSiS 4 single crystals were synthesized using high-temperature flux synthesis. XRD analysis showed that the products are isostructural to CsLaSiS 4 and crystallize in orthorhombic space group Pnma. Absorption spectra were studied at room temperature, and photoluminescence properties were examined in the temperature range of 5–310 K. The energy of interband transitions E g = 3.75 eV was determined at room temperature in the Tauc model. At room temperature, only a non-elementary d → f emission band of Ce+3 ions was observed in the 520 nm region. The luminescence kinetics upon excitation by a pulsed cathode beam or X-ray synchrotron radiation exhibited a dominant nanosecond component. Decay time, as well as build-up time, decreased with increasing concentration of Ce+3 ions. Concentration quenching of Ce+3 emission was not observed up to 11.9 mol% of Ce+3 ions. At a low temperature of 5 K, new wide emission bands at 422 and 688 nm appeared in the photoluminescence spectrum. It is shown that the 422 nm band in the photoluminescence spectrum corresponds to host emission, specifically the luminescence of self-trapped excitons (STE). The 688 nm emission band corresponds to defect-related luminescence. STE emission is quenched according to the Mott law at temperatures above 26 K with an activation energy of 20 meV. An efficient energy transfer channel from the STE to the Ce+3 ion via the radiative resonance mechanism is observed. The emission of Ce+3 ions and defect-related luminescence can be excited by the intracenter way, due to electron-hole recombination, or by the creation of defect bound excitons. Based on the obtained spectroscopic data, a band scheme illustrating the processes of relaxation of electronic excitations at T = 5 K in Ce+3 doped CsLaSiS 4 crystals is proposed. [Display omitted] • Ce+3 doped CsLaSiS 4 single crystals were obtained through high-temperature flux synthesis. • Inter configurational d-f transitions in Ce3+ ions were studied upon both UV- and X-ray excitation. • Luminescence kinetic studies were conducted using a pulsed cathode beam and X-ray synchrotron radiation. • Self-trapped excitons, defect-bound excitons, and impurity luminescence were observed at T = 5 K. [ABSTRACT FROM AUTHOR]