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Growth mechanisms of F4-TCNQ on inorganic substrates and nanostructures
摘要： The organic semiconductor tetrafluorotetracyanoquinodimethane (F4-TCNQ) is a promising candidate for the doping of organic semiconductors, two-dimensional materials and inorganic compounds, such as ZnO, and also to enhance the charge carrier injection at contacts in organic electronics. In order to evaluate its applicability as a functionalization material or as an electrically active part in devices, we present a systematic study on the growth mode of F4-TCNQ beyond the first few monolayers on different inorganic substrates that cover a broad variety regarding their physical, chemical and morphological surface properties. The materials used are silicon, silicon carbide, graphene on silicon, sapphire, nanocrystalline diamond, as well as gallium nitride (GaN) layers and nanowire arrays. While the surface termination influences the shape and morphology of the islands of F4-TCNQ which form on all substrates investigated, no significant dependence of the growth mode on the substrate doping type and concentration is observed. GaN nanowires are found to act as nucleation sites for F4-TCNQ islands and to be covered by few monolayers of F4-TCNQ forming a closed coaxial shell. In conclusion, F4-TCNQ is identified to nucleate via Stranski-Krastanov growth consisting of monolayers and islands of different size and shape. The findings in this work provide basic growth information for the implementation of F4-TCNQ as functionalization material for nanowire-based applications.
关键词： GaN nanowires,surface functionalization,growth mode,organic semiconductors,organic electronics,surface doping,F4-TCNQ
更新于2025-09-23 15:21:01
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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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Towards efficient and stable perovskite solar cells employing non-hygroscopic F4-TCNQ doped TFB as the hole-transporting material
摘要： Designing an efficient and stable hole transport layer (HTL) material is one of the essential ways to improve the performance of organic–inorganic perovskite solar cells (PSCs). Herein, for the first time, an efficient model of a hole transport material (HTM) is demonstrated by optimized doping of a conjugated polymer TFB (poly[(9,9-dioctylfluorenyl-2,7-diyl)-co-(4,4’-(N-(4-sec-butylphenyl)diphenylamine)]) with a non-hygroscopic p-type dopant F4-TCNQ (2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane) for high-efficiency PSCs. The PSC with the F4-TCNQ doped TFB exhibits the best power conversion efficiency (PCE) of 17.46%, which surpasses that of the reference devices, i.e., 16.64 (LiTFSI + TBP-doped Spiro-OMeTAD as the HTM) and 11.01% (LiTFSI + TBP-doped TFB as the HTM). F4-TCNQ doped TFB was believed to favor efficient charge and energy transfer between the perovskite and the hole transport layer and to reduce charge recombination as evidenced by steady-state photoluminescence (PL) and time-resolved photoluminescence (TRPL) analysis. Moreover, the hydrophobic nature of F4-TCNQ contributed to enhancing the stability of the device under ambient conditions with a RH of 45%. The device reported herein retained ca. 80% of its initial efficiency after 10 days, significantly superior to both LiTFSI + TBP-doped Spiro-OMeTAD (ca. 30%) and LiTFSI + TBP-doped TFB (ca. 10%) based counterparts. This simple yet novel strategy paves the way for demonstrating a promising route for a wide range of highly efficient solar cells and other photovoltaic applications.
关键词： stability,perovskite solar cells,F4-TCNQ,hole transport material,TFB,efficiency
更新于2025-09-16 10:30:52
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Molecular Doping for Hole Transporting Materials in Hybrid Perovskite Solar Cells
摘要： Hybrid lead halide perovskites have been revolutionary in the photovoltaic research field, reaching efficiencies comparable with the most established photovoltaic technologies, although they have not yet reached their competitors’ stability. The search for a stable configuration requires the engineering of the charge extraction layers; in this work, molecular doping is used as an efficient method for small molecules and polymers employed as hole transport materials in a planar heterojunction configuration on compact-TiO2. We proved the viability of this approach, obtaining significantly increased performances and reduced hysteresis on compact titania-based devices. We investigated the photovoltaic performance correlated to the hole transport material structure. We have demonstrated that the molecular doping mechanism is more reliable than oxidative doping and have verified that molecular doping in polymeric hole transport materials leads to highly efficient perovskite solar cells, with long-term stability.
关键词： stability,perovskite solar cell,hysteresis,F4-TCNQ,molecular doping
更新于2025-09-16 10:30:52
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Molecular adsorption and strain-induced ferromagnetic semiconductor-metal transition in half-hydrogenated germanene
摘要： Very recently, half-hydrogenated germanene has been achieved in an experiment. In this paper, we investigate the effects of tetracyanoquinodimethane (TCNQ) molecular adsorption and strain on the electronic properties of half-hydrogenated germanene through first-principles. As an electron-acceptor molecule, TCNQ is exploited to non-covalently functionalize the half-hydrogenated germanene. However, this physical adsorption induces a ferromagnetic semiconductor–metal transition in half-hydrogenated germanene due to charge transfer from the substrate to the TCNQ molecule. More importantly, the superstructure of half-hydrogenated germanene/TCNQ is extremely sensitive to biaxial tensile strain. Under the biaxial tensile strain of 0.25%, the ferromagnetic semiconductor–metal transition induced by molecular adsorption can surprisingly be overturned. Meanwhile, a strong p-type doping is exhibited. Remarkably, it would return from a ferromagnetic semiconductor to a metal again when the biaxial tensile strain increases to 1.5%. Our analysis based on the structural and electronic properties of half-hydrogenated germanene/TCNQ indicates that such metal–semiconductor–metal transition in half-hydrogenated germanene/TCNQ under biaxial tensile strain may originate from the strong local deformation, resulting in the energy of the valence band maximum decreasing below or increasing above the Fermi level.
关键词： ferromagnetic semiconductor–metal transition,p-type doping,half-hydrogenated germanene,TCNQ molecular adsorption,biaxial tensile strain
更新于2025-09-10 09:29:36
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Building two-dimensional metal–organic networks with tin
摘要： We show that Sn atoms combined with organic ligands can be used to build 2D coordination networks on Au(111) surfaces. The use of metal–organic bonding has been recognized as a powerful strategy for the generation, directly on solid surfaces, of 2D modular functional materials with potential application in catalysis, organic electronics, and magnetism. This has lead to the important progress observed in recent years in the engineering of a great variety of surface-supported 2D metal–organic networks (MONs). In this Communication, we report the first example of a surface-confined Sn-based MON. With only a few studies of surface-supported MONs based on p-block metals reported in the literature, the possibilities of building modular 2D MONs based on this group of metals remains almost unexplored to date. Tin, with formal oxidation states 2 and 4, forms a large diversity of metal–organic compounds (organotin compounds) which have a wide range of applications ranging from all sorts of biological activity to industrial catalytic processes. Organotin compounds have also attracted the attention of the condense-matter community, especially since stanene-cyanide was proposed as a candidate topological-insulator material. We thus investigated the synthesis, directly on Cu(100) and Au(111) surfaces, of Sn-based MONs using 7,7,8,8-tetracyanoquinodimethane (TCNQ) molecules as ligands.
关键词： Au(111) surfaces,TCNQ molecules,2D coordination networks,Sn-based MON,metal–organic bonding
更新于2025-09-04 15:30:14