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Conjugated Polymer Controlled Morphology and Charge Transport of Small-Molecule Organic Semiconductors
摘要： In this study, we report an effective approach to tune the crystallization, microstructure and charge transport of solution-processed organic semiconductors by blending with a conjugated polymer additive poly(3-hexylthiophene) (P3HT). When 6,13-bis(triisopropylsilylethynyl) pentacene (TIPS pentacene) was used as a model semiconductor material to mix with different amount of P3HT, their intermolecular interactions led to distinctive TIPS pentacene film morphologies, including randomly-oriented crystal ribbons, elongated needles with enhanced long-range order, and grass-like curved microwires with interlinkages. Each type of morphology was found to further correlate to considerably different charge transport and device performance. As compared to pristine TIPS pentacene devices, bottom-gate, top-contact OTFTs with 2% in weight P3HT additive showed a 2-fold and 5-fold improvement of average field-effect mobility and performance consistency (defined as the ratio of average mobility to the standard deviation), respectively. The improvement in transistor electrical performance can be attributed to the combined effect of enhanced crystal orientation and uniformity, as well as increased areal coverage. This work can be applied beyond the particular example demonstrated in this study and to tune the charge transport of other small-molecule organic semiconductors in general.
关键词： OTFTs,TIPS pentacene,organic semiconductors,film morphology,P3HT,charge transport,conjugated polymer
更新于2025-09-19 17:13:59
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Investigating the influence of the solution-processing method on the morphological properties of organic semiconductor films and their impact on OLED performance and lifetime
摘要： The morphological properties of organic semiconductor films deposited by blade coating and spin coating were investigated. The effect of these solution coating methods in fabricating the hole transport layer (HTL) and emissive layer (EML) of OLEDs was also examined. Transient photoluminescence measurements showed that blade-coated films have longer exciton lifetimes than spin-coated films, indicating that blade coating leads to films with less aggregated and more uniform morphologies. OLEDs with a blade-coated CBP:Ir(ppy)3 EML exhibited an external quantum efficiency (EQE) at 20 mA/cm2 of 8.6 % versus 6.4 % in case of device with the same structure but with a spin-coated EML. Additionally, the blade coated CBP:Ir(ppy)3-based device showed a decrease in electroluminescence emission peak by about 52% from its initial value after 20 min of electrical aging, whereas for the spin-coated device, the decrease was 74%. The higher efficiency and longer lifetime in the blade coated devices is likely a result of a more uniform or less aggregated film morphology. These findings demonstrate that blade coating is a promising solution-based fabrication technique to enable more efficient and longer-lived small molecule, solution-coated OLEDs and organic optoelectronic devices.
关键词： Blade coating,OLEDs,Lifetime,Organic semiconductors,Spin coating,Morphology
更新于2025-09-19 17:13:59
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Optoelectronic and Electronic Properties of Tetracyanoindane for Chemical Doping of Organic Semiconductors
摘要： Chemical doping of organic semiconductors is a common technique used to increase the performance numerous organic electronic and optoelectronic devices. Tetrafluoro-tetracyanoquinodimethane (F4-TCNQ) is one of the most widely known p-dopants having the properties necessary to act as a strong electron acceptor. Despite its strong electron accepting abilities, F4-TCNQ is extremely expensive, making it less than ideal for large-area applications. Here, we introduce a small molecule called Tetracyanoindane (TCI) as a potential p-dopant. Widely known for its role in the field of non-linear optics, its high polarizability arises from the addition of four cyano-groups, which are electron withdrawing groups. The four cyano-groups are also seen in the F4-TCNQ molecule and contributes to the withdrawing strength alongside the four fluorine atoms present. We hypothesize that TCI could have similar accepting strength to F4-TCNQ and could potentially replace it as a cheaper alternative. In this study, Cyclic Voltammetry (CV), UV-Visible-Near Infrared Spectroscopy (UV/Vis/NIR), Photoluminescence (PL), Current-Voltage (IV) measurements analysis was conducted to compare the accepting strength of TCI and F4-TCNQ. Then, the two molecules were added to Poly-3-hexy-thiophene (P3HT) to observe how readily they dope the organic semiconductor.
关键词： p-dopant,F4-TCNQ,Tetracyanoindane,Chemical doping,organic semiconductors
更新于2025-09-16 10:30:52
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Enhancing charge mobilities in self-assembled Na?ˉI halogen bonded organic semiconductors: A design approach based on experimental and computational perspectives
摘要： Charge transport in pyridine-ethynyliodophenyl supramolecules that involve intermolecular halogen bonding is studied by a combined experimental and computational approach. Selective fluorination of the molecules determines their crystallization pattern and is found to potentially increase the charge mobilities in the crystal. We report the synthesis of the molecules, full chemical characterization and resolved crystal structures. Computational analysis of the charge transport is provided to understand at the molecular level the structure-function relationships determining the charge mobilities. Combination of selective fluorination, halogen bonding motif and increased π system is highlighted as bearing the potential to achieve both enhanced hole and electron mobilities.
关键词： Selective fluorination and phenylation,Hole and electron mobility,Halogen bonding,Organic semiconductors,Charge transport,Density functional theory
更新于2025-09-16 10:30:52
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D‐A Type Pendant Conjugated Molecules based on Triazine Center with Depressed Intramolecular Charge Transfer Characteristics as Gain Media for Organic Semiconductor Lasers
摘要： A set of fluorene-capped pendant conjugated molecules (T-m and T-p), which consist of triazine center with three carbazole substituents as the donor-acceptor (D-A) type pendant structure, were designed, synthesized and investigated as gain media for organic semiconductor lasers (OSLs). Particularly, varying the capping positions of the fluorene units onto the pendant core structures results in obviously different intramolecular charge transfer (ICT) properties, whereas T-m manifested depressed ICT characteristic and high fluorescence quantum yield. The lowest ASE threshold in neat films was recorded of 1.9 μJ/cm2 for T-m and 83.8 μJ/cm2 for T-p, respectively, which indicated that depressed ICT characteristic in the case of T-m helps to enhance the ASE properties. Remarkably, the ASE threshold remained almost unchanged and the ASE spectra showed very small shifts (within 1 nm) for T-m with film samples annealed up to 180°C in open air. In contrast, its linear counterpart 2FEtCz-m showed obviously increased ASE threshold upon annealing above 100°C. The results suggest that the selective construction of conjugated pendant molecules with depressed ICT characteristics is beneficial for finely modulating the optical and electrical properties as well as improving the thermostability and photostability, which manifests the great potentials as robust gain media for OSLs.
关键词： Organic semiconductors,Amplified spontaneous emission (ASE),Organic semiconductor lasers,Pendant conjugated molecules,Intramolecular charge transfer (ICT)
更新于2025-09-12 10:27:22
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Characterization of vacuum-deposited films of hexachloro-substituted subphthalocyanines for photovoltaic applications
摘要： The thin film properties of the new hexachloro-pyrazinosubporphyrazine compound, Cl6-pSubPz, were studied in comparison with those of an effective molecular acceptor, hexachloro-substituted subphthalocyanine, Cl6-SubPc. The latter compound is widely used in organic photovoltaics as electron acceptor (n-type layer). It was shown that with high-vacuum sublimation Cl6-pSubPz forms stable, smooth and highly textured films on many functional inorganic surfaces. The position of the main electronic absorption band (Q-band) of this compound in the visible range coincides with the maximum of the solar spectrum. Specific conductivity of the sublimed films of both studied compounds lies in the same range, but its thermal activation energy for Cl6-pSubPz is two times higher than for Cl6-SubPc.
关键词： Morphology,Thin films,Spectra,Organic semiconductors,Subphthalocyanines
更新于2025-09-12 10:27:22
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The Cost of Converting Excitons into Free Charge Carriers in Organic Solar Cells
摘要： Efficient exciton dissociation and subsequent generation of free charge carriers at the organic donor-acceptor interface requires a number of electron transfer processes. It is a common view that these steps result in an unavoidable energy loss in organic photovoltaic devices, not present in other types of solar cells. The currently best performing organic solar cells with power conversion efficiencies over 16% challenge this view and no interfacial charge-transfer states with significantly lower energy than the strongly absorbing singlet states are detected within the gap of the used donor and acceptor materials. This perspective will discuss implications, the remaining sources of energy loss and open questions to be solved to achieve power conversion efficiencies over 20%.
关键词： photo-physics,Organic semiconductors,charge-transfer,Photovoltaics,spectroscopy
更新于2025-09-12 10:27:22
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Modeling Thin Film Solar Cells: From Organic to Perovskite
摘要： Device model simulation is one of the primary tools for modeling thin film solar cells from organic materials to organic–inorganic perovskite materials. By directly connecting the current density–voltage (J–V) curves to the underlying device physics, it is helpful in revealing the working mechanism of the heatedly discussed organic–inorganic hybrid perovskite solar cells. Some distinctive optoelectronic features need more phenomenological models and accurate simulations. Herein, the application of the device model method in the simulation of organic and organic–inorganic perovskite solar cells is reviewed. To this end, the ways of the device model are elucidated by discussing the metal–insulator–metal picture and the equations describing the physics. Next, the simulations on J–V curves of organic solar cells are given in the presence of the space charge, interface, charge injection, traps, or exciton. In the perovskite section, the effects of trap states, direct band recombination, surface recombination, and ion migration on the device performance are systematically discussed from the perspective of the device model simulation. Suggestions for designing perovskite devices with better performance are also given.
关键词： perovskites,device models,thin film solar cells,organic semiconductors
更新于2025-09-12 10:27:22
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Donor–Acceptor Distance-Dependent Charge Transfer Dynamics Controlled by Metamaterial Structures
摘要： Capability to control charge transfer dynamics in donor-acceptor molecule is important for efficient optoelectronic devices. Charge transfer dynamics is governed by thermodynamics of donor-acceptor charges in a given dielectric environment. Metamaterial structure has been shown to be able to control charge separation and charge recombination processes via nonlocal effect on dielectric permittivity for a fixed donor-acceptor distance organic film. Here, we report the influence of metamaterial structure on the donor-acceptor distance dependence of electron transfer process occurring in liquid crystalline organic semiconductor thin films. By examining charge recombination rate in three different donor-acceptor distances, it is found that the barrier height β increases from 0.084 ??1 to 0.137 ??1 by 63% in the presence of metal-dielectric multilayered metamaterial structures. Based on Marcus theory on charge transfer process, we show that the further increase of driving force for a larger donor-acceptor distance is mainly responsible for the barrier height increase in the presence of multi-layered metamaterial substrate when compared with glass substrate. This study will provide a significant step forward in enabling more efficient hybrid organic-optoelectronic devices associated with charge transfer process.
关键词： Charge transfer dynamics,Organic semiconductors,Metamaterials,Marcus Theory,Nonlocal effect
更新于2025-09-12 10:27:22
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Synthesis and characterization of vinazene end capped dipyrrolo[2,3-b:2′,3′-e]pyrazine-2,6(1H,5H)-dione small molecules as non-fullerene acceptors for bulk heterojunction organic solar cells
摘要： Two dipyrrolo[2,3-b:2',3'-e]pyrazine-2,6(1H,5H)-dione (PzDP)-based small molecules DPDV and DPEV with PzDP as the core building block and 4,5-dicyano-2-vinylimdazole (vinazene) as end-cap units were synthesized by Heck coupling reaction. The photophysical, electrochemical properties of DPDV and DPEV were investigated and applied as non-fullerene acceptors (NFAs) for solution-processed bulk heterojunction (BHJ) organic solar cells (OSCs). Theoretically evaluated optical and electrochemical properties were well matched with experimental values. Solution processed BHJOSCs employing poly[(4,8-bis[(2-ethylhexyl)oxy]benzo[1,2-b:4,5-b′]dithiophene-2,6-diyl)-alt-(3-fluoro-2-[(2-ethylhexy)carbonyl]thieno[3,4-b]thiophene-4,6-diyl)] (PTB7) as the donor polymer and DPDV/ DPEV as NFAs exhibited short-circuit current density (JSC) of 2.23/ 2.44 mA cm-2, open-circuit voltage (VOC) of 0.54/ 0.55 V, fill factor (FF) of 36.97/ 38.62 and power conversion efficiency (PCE) of 0.45/0.52%, respectively.
关键词： heterocycles,cyclic voltammetry,bulk heterojunction organic solar cells,non-fullerene acceptors materials,organic semiconductors
更新于2025-09-11 14:15:04