1,721,094 research outputs found
Direct Growth of Substrate-Adhered Graphene on Flexible Polymer Substrates for Soft Electronics
No full textThis article describes a novel method of growing graphene directly on a flexible substrate at low polyimide temperatures using plasma-enhanced chemical vapor deposition with a solid aromatic hydrocarbon source, 1,2,3,4tetraphenylnaphthalene (TPN), which acts as the feedstock for graphene growth. TPN is embedded with copper ions that are reduced under the growth conditions to copper nano particles that catalyze the graphene growth and then evaporate to leave pristine graphene. Strong covalent bonds between the TPN film and the flexible substrate, prepared by depositing an aluminum oxide (A120,) layer on a colorless polyimide layer, are generated by exposing the TPN film to ultraviolet/ozone. The TPN/substrate interfacial adhesive bonds impede the sublimation of TPN from the flexible substrate at the growth temperature, and TPN can convert directly to graphene. The synthesized substrate-adhered graphene shows excellent bending stability, with small electrical resistance changes (the resistance R during bending over initial resistance Ro was R/Ro < 1.2 for compressive strain, and R/Ro < 1.4 for tensile strain at e = 4.68%). Graphene is appropriate for use in flexible and transparent electrodes for electronic device applications. The proposed method for directly synthesizing substrate-adhered graphene on a flexible substrate is expected to have wide applications in flexible and wearable electronics.11Nsciescopu
Effective Use of Electrically Insulating Units in Organic Semiconductor Thin Films for High-Performance Organic Transistors
No full textThe electrical properties of organic semiconductors (OSCs), whether they are conjugated small molecules or polymers, can be tailored by incorporating electrically insulating units (EIUs), which are organic moieties consisting of nonconjugated units. EIUs can be introduced to a thin film by synthetically connecting them to the otherwise conjugated OSC molecules or by blending them in as separate EIU molecules with the OSCs during the thin-film fabrication process. The engineered EIUs are capable of imparting various additional functions to the OSC thin film and improving their electrical properties. In this review article, a comprehensive overview of various effects of EIUs on OSC thin films and their consequent electrical performance when used as active layers in organic field-effect transistors (OFETs) is provided. A broad range of studies of the synthetic approaches of incorporating EIUs, such as those using side chains, block copolymers, and conjugation-break spacers, and of the blending approaches with organic insulators is discussed. Finally, a brief summary and perspectives for future research in this field are presented.1120sciescopu
Surface Passivation by Sulfur-Based 2D (TEA)2PbI4 for Stable and Efficient Perovskite Solar Cells
No full textPerovskite solar cells (PSCs) with superior performance have been recognized as a potential candidate in photovoltaic technologies. However, defects in the active perovskite layer induce nonradiative recombination which restricts the performance and stability of PSCs. The construction of a thiophene-based 2D structure is one of the significant approaches for surface passivation of hybrid PSCs that may combine the benefits of the stability of 2D perovskite with the high performance of three-dimensional (3D) perovskite. Here, a sulfur-rich spacer cation 2-thiopheneethylamine iodide (TEAI) is synthesized as a passivation agent for the construction of a three-dimensional/two-dimensional (3D/2D) perovskite bilayer structure. TEAI-treated PSCs possess a much higher efficiency (20.06%) compared to the 3D perovskite (MA0.9FA0.1PbI3) devices (17.42%). Time-resolved photoluminescence and femtosecond transient absorption spectroscopy are employed to investigate the effect of surface passivation on the charge carrier dynamics of the 3D perovskite. Additionally, the stability test of TEAI-treated perovskite devices reveals significant improvement in humid (RH similar to 46%) and thermal stability as the sulfur-based 2D (TEA)2PbI4 material self-assembles on the 3D surface, making the perovskite surface hydrophobic. Our findings provide a reliable approach to improve device stability and performance successively, paving the way for industrialization of PSCs.11Ysciescopu
Acceptor-donor-acceptor molecule processed using polar non-halogenated solvents for organic field-effect transistors
No full textNon-chlorinated solvents, especially polar non-chlorinated solvents, are highly desirable for the fabrication of organic field-effect transistors (OFETs) because they do not create environmental and health issues. In this paper, four polar non-chlorinated solvents, namely, tetrahydrofuran (THF), ethyl acetate (EtAc), acetone (AT), and 2-methyltetrahydrofuran (2-MTHF) were used to fabricate high-performance acceptor-donor-acceptor small molecules (IDTT-IDD-N) for OFETs. The effects of polar non-chlorinated solvents regarding optical properties, device performances, and microstructures were investigated in detail. High-performance OFETs were demonstrated with the hole mobilities of up to 1.01, 1.49, 2.40, and 0.81 cm(2) V-1 s(-1) for the THF, EtAc, AT, and 2-MTHF-processed devices, respectively. This work indicates that the IDTT-IDD-N-based OFETs fabricated from polar non-chlorinated solvents have potential applications in high-performance and environmentally friendly organic electronics.11Nsciescopu
Regulating the Donor–Acceptor Interfaces to Reduce Trap Density for Efficient Indoor Organic Solar Cells
No full textOrganic solar cells (OSCs) are promising candidates for powering the Internet of Things and off-grid devices due to the rapid improvement in power conversion efficiency under indoor light. However, the reported indoor devices are often taken straightforwardly from the champion solar cells under AM1.5 G irradiance without further optimization or more target design, which may underestimate their performance due to trap-assisted charge recombination caused by discrepancies in incident light spectrum and intensity. Herein, It is identified that regulation of donor–acceptor interfaces is critical for reducing trap density in the active layer and thus improving the performance of indoor OSCs. By investigating bulk heterojunction and bilayer devices composed of PM6 and ITIC or ITIC-2 F, reduced trap density is demonstrated by mitigation of the structural disorder of the active layer, leading to improved open-circuit voltage. Additionally, the trap depth has a negligible effect on the device's performance with indoor light illumination. The results establish the correlations between donor–acceptor interfaces and charge recombination losses in bulk heterojunction and bilayer OSCs under indoor light, providing novel optimization guidelines for high-performing indoor OSCs. © 2022 Wiley-VCH GmbH.11Nsciescopu
Balancing the performance and stability of organic photodiodes with all-polymer active layers
No full textOrganic photodiodes (OPDs) have emerged as a potential alternative for inorganic photodiodes in light-detection technology due to their unique properties such as lightweight, flexibility, and tunable absorption range. However, the stability of OPDs is one of the main issues preventing the commercialization of OPDs. Herein, we performed a detailed characterization study of OPDs composed of all-polymer and polymer donors/small molecular acceptors to evaluate the detectivity and stability of devices. The small molecule acceptor Y5-Br and its polymerized counterpart PY-IT were selected to minimize the energy and absorption differences and paired with PM6. We found that the Y5-Br based device exhibited a higher detectivity and a lower dark current density due to the lesser extent of the trap density, whereas the PY-IT based device demonstrated a faster response time and impressive thermal/electrical stability. In addition, the analysis of the photosensitive layer morphology reveals that the all-polymer films showed remarkable thermal tolerance. In contrast, the thermal treatment resulted in apparent polymer and small molecule aggregations in the polymer-small molecule counterpart, leading to large scale phase segregations. Our findings suggest that the all-polymer composition is an efficient strategy to improve the stability of OPDs and provide a useful guidance for the commercial application of OPDs in the future.11Nsciescopu
Rational molecular design for isoindigo-based polymer semiconductors with high ductility and high electrical performance
No full textAchieving good electrical properties and ductility of polymer semiconductors has always been challenging. In this work, a series of isoindigo derivative-based conjugated polymers was studied in an effort to gain a better understanding of the influence of polymer main and side chain structures on their electrical and mechanical properties. The results suggested that the introduction of alkyl side chains onto the donors can significantly enhance the mechanical properties of isoindigo-based polymers; however, the electrical properties of the films greatly deteriorated due to the large steric hindrance by the chain. The insertion of strong electron-withdrawing units, such as benzodifurandione, into the isoindigo chain during the synthesis of a bis(2-oxoindolin-3-ylidene)-benzodifuran-dione (BIBDF)-based polymer (PBIBDF-BT) significantly boosted the electrical properties of the films without decreasing their mechanical properties. The crack onset in PBIBDF-BT thin films was observed at 50% tensile strain. In addition, PBIBDF-BT thin films exhibited bipolar transport properties with both electron and hole mobilities greater than 0.1 cm(2) V-1 s(-1) at 100% strain. It is found that the improvement of PBIBDF-BT performance is attributed to its proper molecular structure. The long alkyl side chains significantly increase the ductility of PBIBDF-BT thin films, and the strong electron-withdrawing BIBDF unit in the main chains enhances the local aggregation, resulting in a significant increase in mobility. These results indicate that the mechanical and electrical properties of conjugated polymers could simultaneously be improved through reasonable molecular design.11Nsciescopu
One-step synthesis of an acceptor-donor-acceptor small molecule based on indacenodithieno[3,2-b]thiophene and benzothiadiazole units for high-performance solution-processed organic field-effect transistors
No full textWe reported a one-step synthesis of a high-performance acceptor-donor-acceptor small molecule based on indacenodithieno[3,2-b]thiophene (IDTT) as the donor unit and benzothiadiazole (BT) as the acceptor unit. The thermal, optical, and electrochemical properties and crystal structure of the small molecule were systematically investigated. The solution-processed organic field-effect transistors exhibited nearly ideal characteristics in the saturation regime with an excellent hole mobility (2.01 cm(2) V-1 s(-1)), a high I-on/I-off ratio (>10(6)), and a negligible threshold voltage (-2 to -4 V).11Nsciescopu
Propeller-shaped small molecule acceptors containing a 9, 9′-spirobifluorene core with imide-linked perylene diimides for non-fullerene organic solar cells
No full textThree-dimensional (3D) non-fullerene small molecule acceptors with imide-linked perylene diimides (iPDI) on a 9,90'-spirobi[9H-fluorene] core were designed, synthesized and characterized for use in organic solar cells. The best power conversion efficiency of 5.31% is obtained using SF-iPDI2 in a solution-processed bulk heterojunction solar cell. These results demonstrate that PDI derivatives with 3D molecular structures could serve as high-performance electron acceptors in non-fullerene solar cells.1112sciescopu
Polarization-Dependent Photoinduced Bias-Stress Effect in Single-Crystal Organic Field-Effect Transistors
No full textPhotoinduced charge transfer between semiconductors and gate dielectrics can occur in organic field-effect transistors (OFETs) operating under illumination, leading to a pronounced bias-stress effect in devices that are normally stable while operating in the dark. Here, we report an observation of a'polarization-dependent photoinduced bias-stress effect in two" prototypical single-crystal OFETs, based on rubrene and tetraphenylbis(indolo{l,2-alpha})quinolin. We find that the decay rate of the source-drain current in these OFETs under, illumination is a periodic function of the polarization angle of incident photoexcitation with respect to the crystal axes, with a periodicity of n. The angular positions of maxima and minima of the bias-stress rate match those of the optical absorption coefficient of the corresponding crystals. The analysis of the effect shows that it stems from a charge transfer of "hot" holes, photogenerated in the crystal within a very short thermafization length (MLT mu m) from the semiconductor-dielectric interface. The observed phenomenon is a type of intrinsic structure-property relationship, revealing how molecular packing affects parameter drift in organic transistors under illumination. We also demonstrate that a photoinduced charge transfer in OFETs can be used for recording rewritable accumulation channels with an optically defined geometry and resolution, which can be used in a number of potential applications.113sciescopu
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