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A Pentacene-based Nanotube Displaying Enriched Electro/Photochemical Activities
摘要： We report the first synthesis of a pentacene-based nanotube displaying a tubular conformation in solution. The product possesses a triangular prismatic structure with three pentacene chromophores connected by a rigid, triangular backbone. Steady-state and time-resolved spectroscopic analyses revealed that the nanotube exhibits enriched electro/photochemical activities due to the close proximity of the three pentacene chromophores, which allows for efficient intramolecular singlet fission and long-lived triplet excitons.
关键词： photochemistry,pentacene,singlet fission,nanotube,triplet excitons,electrochemistry
更新于2025-09-23 15:21:01
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On the absence of triplet exciton loss pathways in non-fullerene acceptor based organic solar cells
摘要： We investigate the viability of highly efficient organic solar cells (OSCs) based on non-fullerene acceptors (NFA) by taking into consideration efficiency loss channels and stability issues caused by triplet excitons (TE) formation. OSCs based on a blend of the conjugated donor polymer PBDB-T and ITIC as acceptor were fabricated and investigated with electrical, optical and spin-sensitive methods. The spin-Hamiltonian parameters of molecular TEs and charge transfer TEs in ITIC e.g., zero-field splitting and charge distribution, were calculated by Density Functional Theory (DFT) modelling. In addition, the energetic model describing the photophysical processes in the donor-acceptor blend was derived. Spin-sensitive photoluminescence measurements prove the formation of charge transfer (CT) states in the blend and the formation of TEs in the pure materials and the blend. However, no molecular TE signal is observed in the completed devices under working conditions by spin-sensitive electrical measurements. The absence of a molecular triplet state population allows to eliminate a charge carrier loss channel and irreversible photooxidation facilitated by long-lived triplet states. These results correlate well with the high power conversion efficiency of the PBDB-T:ITIC-based OSCs and their high stability.
关键词： triplet excitons,Density Functional Theory,organic solar cells,non-fullerene acceptors,photoluminescence detected magnetic resonance,electrically detected magnetic resonance
更新于2025-09-19 17:13:59
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Achieving high-performance phosphorescent organic light-emitting diodes using thermally activated delayed fluorescence with low concentration
摘要： We fabricated phosphorescent organic light-emitting diodes (PhOLEDs) using thermally activated delayed fluorescence (TADF) material 10,10'-(4,4'-sulfonylbis(4,1-phenylene)) bis(9,9-dimethyl-9,10-dihydroacridine) (DMAC-DPS) with low concentration, which showed better performance compared with 1,3-bis(carbazole-9-yl) benzene (mCP) based devices. When the concentration of DMAC-DPS was 1wt%, the driving voltage of the device was only 3.3 V at 1 000 cd/m2, and the efficiency and lifetime of the device were effectively improved compared with those of mCP based devices. The result indicated that DMAC-DPS could effectively improve the performance of phosphorescent devices. We believe that the better device performance can be attributed to the optimization of the energy transfer process in the emitter layer and lifetime of triplet excitons by DMAC-DPS. The study may provide a simple and effective strategy to achieve high-performance OLEDs.
关键词： DMAC-DPS,thermally activated delayed fluorescence,triplet excitons,energy transfer,phosphorescent organic light-emitting diodes
更新于2025-09-16 10:30:52
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Lowering the power of OLEDs
摘要： Lower power OLED displays could emerge from the latest work from an international collaboration between researchers at RIKEN, the University of California San Diego, the University of Tokyo, and the Institute for Molecular Science. Organic light emitting diodes (OLEDs) have been with us for many years now. They offer many advantages over other types of display based on inorganic LEDs and liquid crystal displays. They can be ?exible, thin, and preclude the need for a power-draining backlight. Writing in the journal Nature, the team explains how they have found a new way to manipulate the “excitons”-the electron-hole pairs that are key for charge transport within an OLED. The team points out that a current passing through an OLED device creates exciton pairs and when these drop down to a lower energy level, they emit visible light in a quantum process. OLED excitons arise in one of two patterns - the spins are either in the same direction or opposing. The former, so-called triplet excitons, are three times more common than the latter, the singlet excitons. Singlet excitons are formed only at higher energy and they can ultimately convert into triplets, but it would cut energy costs in a device if singlets were not formed at all. The team has now demonstrated that lowering the voltage so that only triplets are formed is possible where it was always assumed this would not work. They used electroluminescence measurements with a scanning tunneling microscope (STM) and an optical detection system to observe the formation of excitons. A model system with a single, isolated molecule of the organic semiconductor 3, 4, 9, 10-perylenetetracarboxylic-dianhydride (PTCDA) on metal-supported ultrathin insulating ?lm was key to their understanding. By imparting a negative charge to this supported molecule, they could use the STM tip to induce luminescence in the molecule, and monitored record the emission spectrum of the resulting excitons. Critically, at low voltage, only triplets form. Theoretical calculations support the suggested mechanism.
关键词： OLEDs,scanning tunneling microscope,PTCDA,singlet excitons,electroluminescence,triplet excitons,excitons
更新于2025-09-12 10:27:22
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Time dependent correlations of entangled states with nondegenerate branches and possible experimental realization using singlet fission
摘要： The spin-entangled exciton states produced by singlet fission provide an experimental route to generate entangled states with nondegenerate branches. Nondegenerate entangled pair states possess an internal "clock" that leads to quantum beating in various detected quantities. The implications of this internal clock for Bell’s inequality measurements and correlated particle detection are analyzed using two- and three-state spin models. In a Bell’s inequality experiment, we find that the choice of detection times can determine whether quantum or classical correlations are observed. The conditions under which the detection events could be time- or spacelike separated are analyzed in order to clarify how the temporal evolution of one particle can influence the time-dependent detection probability of the other. Possible routes to the detection of individual correlated triplet excitons are discussed, emphasizing both physical questions concerning the separation and propagation of triplet excitons over macroscopic distances and experimental challenges concerning decoherence, detection, and interpretation of the signals. We argue that spin-entangled triplet exciton states produced by singlet fission could provide a new way to probe entangled state detection and collapse, complementing schemes based on polarization-entangled photon states.
关键词： detection,Bell’s inequality,correlated particle detection,spin-entangled exciton states,nondegenerate branches,triplet excitons,quantum beating,singlet fission,decoherence
更新于2025-09-12 10:27:22
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Triplet management for efficient perovskite light-emitting diodes
摘要： Perovskite light-emitting diodes are promising for next-generation lighting and displays because of their high colour purity and performance1. Although the management of singlet and triplet excitons is fundamental to the design of efficient organic light-emitting diodes, the nature of how excitons affect performance is still not clear in perovskite2–4 and quasi-two-dimensional (2D) perovskite-based devices5–9. Here, we show that triplet excitons are key to efficient emission in green quasi-2D perovskite devices and that quenching of triplets by the organic cation is a major loss path. Employing an organic cation with a high triplet energy level (phenylethylammonium) in a quasi-2D perovskite based on formamidinium lead bromide yields efficient harvesting of triplets. Furthermore, we show that upconversion of triplets to singlets can occur, making 100% harvesting of electrically generated excitons potentially possible. The external quantum and current efficiencies of our green (527 nm) devices reached 12.4% and 52.1 cd A?1, respectively.
关键词： Perovskite light-emitting diodes,quasi-2D perovskite,external quantum efficiency,triplet excitons,organic cation
更新于2025-09-12 10:27:22
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Impact of the donor polymer on recombination <i>via</i> triplet excitons in a fullerene-free organic solar cell
摘要： The greater chemical tunability of non-fullerene acceptors enables fine-tuning of the donor–acceptor energy level offsets, a promising strategy towards increasing the open-circuit voltage in organic solar cells. Unfortunately, this approach could open an additional recombination channel for the charge-transfer (CT) state via a lower-lying donor or acceptor triplet level. In this work we investigate such electron and hole back-transfer mechanisms in fullerene-free solar cells incorporating the novel molecular acceptor 2,4-diCN-Ph-DTTzTz. The transition to the low-driving force regime is studied by comparing blends with well-established donor polymers P3HT and MDMO-PPV, which allows for variation of the energetic offsets at the donor–acceptor interface. Combining various optical spectroscopic techniques, the CT process and subsequent triplet formation are systematically investigated. Although both back-transfer mechanisms are found to be energetically feasible in both blends, markedly different triplet-mediated recombination processes are observed for the two systems. The kinetic suppression of electron back-transfer in the blend with P3HT suggests that energy losses due to triplet formation on the polymer can be avoided, regardless of favorable energetic alignment.
关键词： charge-transfer state,organic solar cells,triplet excitons,non-fullerene acceptors,recombination mechanisms
更新于2025-09-11 14:15:04