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A Silanea??based Bipolar Host with High Triplet Energy for High Efficiency Deepa??Blue Phosphorescent OLEDs with Improved Device Lifetime
摘要： A high triplet energy host is developed using silane moiety. 9-(4-(triphenylsilyl)dibenzo[b,d]furan-2-yl)-9H-carbazole (SiDBFCz) is designed through extensive density functional theory (DFT) calculations to obtain appropriate hole and electron injection barriers. The chemical hardness and the charge transport characteristics are comprehensively investigated to realize a bipolar host with high triplet energy over 2.9 eV for deep blue phosphorescent organic light-emitting diodes (PHOLEDs). The synthesized SiDBFCz clearly exhibits the bipolar characteristics especially with emitter molecules doped. An external quantum efficiency over 19% without any microcavity optimization is achieved thanks to the good charge balance in the SiDBFCz PHOLED. The device lifetime of the SiDBFCz PHOLED is improved more than 1000%, compared to the unipolar control devices at an initial luminance of 500 cd/m2. The dramatic enhancement of the operational stability of the deep blue PHOLED is also thoroughly investigated in terms of electrochemical stability of host molecules in charged or excited states. The results clearly indicate that the device lifetime is strongly correlated with the bond dissociation energy and the activation energy for the bond dissociation reaction in triplet excited state.
关键词： deep blue phosphorescent OLEDs,bond dissociation energy in triplet excited state,high triplet bipolar host,lifetime
更新于2025-09-16 10:30:52
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Hole Transfer Originating from Weakly Bound Exciton Dissociation in Acceptor–Donor–Acceptor Nonfullerene Organic Solar Cells
摘要： The underlying hole-transfer mechanism in high-efficiency OSC bulk heterojunctions based on acceptor?donor?acceptor (A?D?A) nonfullerene acceptors (NFAs) remains unclear. Herein, we study the hole-transfer process between copolymer donor J91 and five A?D?A NFAs with different highest occupied molecular orbital energy offsets (ΔEH) (0.05?0.42 eV) via ultrafast optical spectroscopies. Transient absorption spectra reveal a rapid hole-transfer rate with small ΔEH, suggesting that a large energy offset is not required to overcome the exciton binding energy. Capacitance?frequency spectra and time-resolved photoluminescence spectra confirm the delocalization of an A?D?A-structured acceptor exciton with weak binding energy. Relative to the hole-transfer rate, hole-transfer efficiency is the key factor affecting device performance. We propose that holes primarily stem from weakly bound acceptor exciton dissociation, revealing a new insight into the hole-transfer process in A?D?A NFA-based OSCs.
关键词： hole-transfer mechanism,organic solar cells,exciton dissociation,ultrafast optical spectroscopies,nonfullerene acceptors
更新于2025-09-12 10:27:22
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High detectivity organic photodetectors in the visible light wavelength with ternary bulk heterojunction
摘要： In this work, we report an ternary bulk heterojunction (t-BHJ) organic photodetectors (OPDs) based on P3HT, PTB7 and PC61BM. The effects of PTB7 added to P3HT:PC61BM on the optical and electrical properties of OPDs were investigated. It is found that when the mass ratio of P3HT:PTB7:PC61BM is 8:2:10, the response spectrum of the active layer is extended to 780 nm, The responsivity (R) and external quantum efficiency (EQE) of the OPDs are reached 178, 291, 241 mA/W and 35%, 68%, 65%, under 630, 530, and 460 nm illumination and ?1 V bias, respectively, and the detectivity (D*) reached 1012 Jones. The results show that the addition of PTB7 with appropriate mass ratio can increases the exciton generation and dissociation probability in P3HT:PC61BM, which increases the photocurrent of the device. In addition, the addition of PTB7 promotes the crystallization of the film, reduces the density of trap defects in the film, and reduces the dark current of the device.
关键词： Microscopic morphology,Organic photodetectors,Ternary bulk heterojunction,Exciton dissociation
更新于2025-09-12 10:27:22
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Influence of single-walled carbon nanotubes induced exciton dissociation improvement on hybrid organic photovoltaic devices
摘要： Torch-plasma-grown single-walled carbon nanotubes (SWCNTs) are integrated with regioregular poly(3-hexylthiophene) (P3HT) and a fullerene derivative 1-(3-methoxycarbonyl) propyl-1-phenyl[6,6]C61 (PCBM) as a hybrid photoactive layer for bulk heterojunction solar cell devices. We demonstrate that molecular information could be accurately obtained by time-of-flight secondary ion mass spectrometry through the hybrid organic photoactive solar cell layers when sputtering is performed using a Cs+ 2000 eV ion source. Furthermore, the photovoltaic (PV) performance of the fabricated devices show an increase in the short-circuit current density (Jsc) and the fill factor (FF) as compared to the pristine devices fabricated without SWCNTs. The best results are obtained with 0.5 wt. % SWCNT loads, where an open-circuit voltage (VOC) of 660 mV is achieved, with a Jsc of 9.95 mA cm?2 and a FF of 54%, leading to a power conversion efficiency of 3.54% (measured at standard test conditions, AM1.5 g). At this optimum SWCNT concentration of 0.5 wt. %, and to further understand the charge-transfer mechanisms taking place at the interfaces of P3HT:PCBM:SWCNT, Jsc is measured with respect to the light intensity and shows a linear dependency (in the double logarithmic scale), which implies that losses in the charge carrier are rather governed by monomolecular recombination. Finally, our results show that our hybrid devices benefit from the fullerene electron accepting nature and from the SWCNT fast electron transportation feature that improve substantially the exciton dissociation efficiency. The influence of the SWCNTs on the Fermi level and the work function of the photoactive composite and its impact on the PV performance is also investigated.
关键词： single-walled carbon nanotubes,bulk heterojunction,PCBM,hybrid organic photovoltaic devices,photovoltaic performance,P3HT,exciton dissociation
更新于2025-09-12 10:27:22
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Fullerene derivative layer induced phase separation and charge transport improvement for inverted polymer solar cells
摘要： The phase separation of donor and acceptor in bulk-heterojunction plays an important role on the exciton dissociation and charge carrier transport, which decides the performance of organic solar cells (OSCs). In this paper, the thin [6,6]-Phenyl-C71-butyric acid methyl ester (PC71BM) layer was incorporated as interlayer between active layer and the polyethylenemine electron transport layer of OSCs to realize high efficiency. Both a high short-circuit current density and fill factor were achieved, resulting in a power conversion efficiency up to 9.17% for the optimal device. The incorporation of PC71BM layer not only induced vertical phase separation of active layer to improve exciton dissociation and charge transfer but also modified surface morphology to increase light absorption of the active layer. This study offers a simple and lost cost strategy to improve performance of OSCs.
关键词： Light absorption,Electron transport,[6,6]-Phenyl-C71-butyric acid methyl ester,Exciton dissociation,Phase separation
更新于2025-09-12 10:27:22
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Structural modification as the pioneer strategy in competition of the porphyrin dye and perovskite solar cells: From dynamics to kinetics of the photovoltaic processes
摘要： Molecular engineering plays a key role in designing ef?cient dye-sensitized/perovskite solar cells (DSSCs/PSCs). Porphyrins have more favorable spectroscopic properties than AZn(COOH)3 perovskites due to their lower chemical hardness. Also, porphyrins are pioneering photosensitizers in exciton formation/dissociation, kinetically. The presence of Zn2t and butadiyne as the linker in the porphyrins and the existence of the electron donors of dimethylammonium and formamidinium in the perovskites improve their photovoltaic properties. Porphyrin dimers have a greater charge transfer distance in comparison to the monomers. However, they show less energy conversion ef?ciency, which may be related to the quenching of the interporphyrin charge transfer. As a consequence, DSSCs based on the porphyrin monomers have a higher ef?ciency than the studied PSCs.
关键词： perovskite solar cells,porphyrin dye,exciton formation/dissociation,molecular engineering,photovoltaic processes
更新于2025-09-11 14:15:04
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Carrier-envelope-phase–controlled molecular dissociation by ultrashort chirped laser pulses
摘要： We demonstrate and characterize that a carrier-envelope-offset-phase (CEP)–controlled ultrashort chirped ?eld is an ef?cient and robust mechanism to modify the dissociation dynamics of molecular hydrogen. Different dissociation pathways are collectively induced and their interference contributes to the kinetic-energy release spectra. Chirping is able to ef?ciently manipulate the interferences of different dissociation pathways. We demonstrate a linear relationship between chirp and CEP dependent dissociation as well as directional electron localization.
关键词： electron localization,molecular dissociation,carrier-envelope-phase,kinetic-energy release spectra,ultrashort chirped laser pulses
更新于2025-09-11 14:15:04
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Water Dissociation and Hydroxyl Ordering on Anatase
摘要： We studied the interaction of water with the anatase TiO2e001T surface by means of scanning tunneling microscopy, x-ray photoelectron spectroscopy, and density functional theory calculations. Water adsorbs dissociatively on the ridges of a (1 × 4) reconstructed surface, resulting in a (3 × 4) periodic structure of hydroxyl pairs. We observed this process at 120 K, and the created hydroxyls desorb from the surface by recombination to water, which occurs below 300 K. Our calculations reveal the water dissociation mechanism and uncover a very pronounced dependence on the coverage. This strong coverage dependence is explained through water-induced reconstruction on anatase TiO2e001T-e1 × 4T. The high intrinsic reactivity of the anatase TiO2e001T surface towards water observed here is fundamentally different from that seen on other surfaces of titania and may explain its high catalytic activity in heterogeneous catalysis and photocatalysis.
关键词： x-ray photoelectron spectroscopy,scanning tunneling microscopy,anatase TiO2,hydroxyl ordering,density functional theory,water dissociation
更新于2025-09-10 09:29:36
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Effect of dielectric and conductive targets on plasma jet behaviour and thin film properties
摘要： A double layer DBD plasma jet driven by a pulsed generator is used for SiOx thin film deposition. The effects of dielectric and conductive targets on discharge behavior and film properties are analyzed. Different optical emission of the plasma jet at different positions are characterized. Film surface morphology, composition properties is studied. Results show that the relative optical emission intensities of Si, O, Ar and N2, as well as and thickness are measured for different targets. The excitation temperature (Texc), vibrational temperature (Tvib) fraction of N2 is added to the working gas (argon) to modulate film growth rate. The electrical property and Texc, Tvib and Trot are higher for the PMMA target between the high voltage electrode and the grounded electrode and rotational temperature (Trot) are calculated. The relationship between the discharge behavior and the film as optical transparency, sufficient insulation strength and scratch resistance1. The application of SiOx films is found in many fields, for example, microelectronics 2, biomedicine 3, food packaging 4 and high voltage insulation5. Plasma-enhanced chemical vapor deposition (PECVD) is one of the well-established methods for (referred to as the H-G region). However, Tvib and Trot appear to be higher on the surface of the copper (conductive) target. The morphology of SiOx film is different: nanoparticles are formed on the PMMA (dielectric) target while the synthesis of SiOx films. It typically involves a low pressure non-thermal plasma system. A low-pressure SiOx film is higher on the copper target. The presence of PMMA at the downstream of the plasma can be dense amorphous film is formed on the copper target. With the same depositing parameters, the thickness of the through the H-G region. Although the presence of a dielectric target enhances the discharge in the H-G region, considered as a small capacitor with a large resistance, which inhibits the current into the primary circuit passing the charge accumulation on the PMMA surface limits the film growth. These results may contribute to the development of next-generation plasma surface modification technologies for diverse applications in electronics, Siloxane (SiOx) films are of great interest because of their excellent physical and chemical properties such
关键词： Target conductivity,Plasma jet,Film deposition,TEOS dissociation,Discharge behavior
更新于2025-09-10 09:29:36
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Dissociating diatomic molecules in ultrafast and intense light
摘要： An ab initio theory is devised for the quantum dynamics of molecules undergoing multiple ionization in ultrafast and intense light. Specifically, the intertwined problem of photoionization, radiative, and electronic transitions in the course of dissociation is addressed which arises, e.g., when molecules are exposed to xuv light or x rays from free electron lasers or attosecond light sources, but the approach is equally useful in optical strong-field physics. The coherent interaction of the molecule with the light in a specific charge state is also treated. I set out from an abstract formulation in terms of the quantum optical notion of system-reservoir interaction using a master equation in Lindblad form and analyze its short-time approximation. First, I express it in a direct sum rigged Hilbert space for an efficient solution with numerical methods for systems of partial differential equations. Second, I derive a treatment via quantum Monte Carlo wave packet (MCWP) propagation. The formalism is concretized to diatomic molecules in Born-Oppenheimer approximation whereby molecular rotation is disregarded. The numerical integration of the master equation is carried out with a suitably factored density matrix that exploits the locality of the Hamiltonian and the Lindblad superoperator with respect to the internuclear distance. The formulation of the MCWP for molecules requires a thorough analysis of the quantum jump process; namely, the dependence on the continuous distance renders a straight wave packet promotion useless and, instead, a projected outer product needs to be employed involving an integrated quantum jump operator.
关键词： Ultrafast and intense light,Born-Oppenheimer approximation,Dissociation of diatomic molecules,Quantum Monte Carlo algorithm,Master equation in Lindblad form
更新于2025-09-10 09:29:36