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Intrinsic Carrier Transport of Phase-Pure Homologous 2D Organolead Halide Hybrid Perovskite Single Crystals
摘要： This work reveals the intrinsic carrier transport behavior of 2D organolead halide perovskites based on phase-pure homologous (n = 1, 2, and 3) Ruddelsden–Popper perovskite (RPP) (BA)2(MA)n?1PbnI3n+1 single crystals. The 2D perovskite field effect transistors with high-quality exfoliated 2D perovskite bulk crystals are fabricated, and characteristic output and transfer curves are measured from individual single-crystal flakes with various n values under different temperatures. Unipolar n-type transport dominated the electrical properties of all these 2D RPP single crystals. The transport behavior of the 2D organolead halide hybrid perovskites exhibits a strong dependence on the n value and the mobility substantially increases as the ratio of the number of inorganic perovskite slabs per organic spacer increases. By extracting the effect of contact resistances, the corrected mobility values for n = 1, 2, and 3 are 2 × 10?3, 8.3 × 10?2, and 1.25 cm2 V?1 s?1 at 77 K, respectively. Furthermore, by combining temperature-dependent electrical transport and optical measurements, it is found that the origin of the carrier mobility dependence on the phase transition for 2D organolead halide perovskites is very different from that of their 3D counterparts. Our findings offer insight into fundamental carrier transport behavior of 2D organic–inorganic hybrid perovskites based on phase-pure homologous single crystals.
关键词： solution growth,field-effect transistors,photoluminescence,intrinsic charge transport,2D RPP single crystals
更新于2025-09-10 09:29:36
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Enhanced Electron Transport in Rutile TiO2 Nanowires via H2S-Assisted Incorporation of Dissolved Silicon for Solar-Driven Water Splitting
摘要： Si-doping is an effective approach to enhance the electron transport and the photocatalytic activity of photocatalyst. In this study, for the first time the silicate glass such as fluorine-doped tin oxide (FTO) glass substrate is used as the silicon source for preparing Si-doped TiO2 photoanodes. First, the rutile TiO2 nanowires (NWs) were grown on FTO glass substrates by hydrothermal reaction, accompanying with the gradual dissolution of glass to generate soluble Si dopant incorporated into TiO2 NWs. Second, the TiO2 NWs were reduced to form the Ti3+ by H2S reduction. Finally, the Si-doped TiO2 photoanodes with higher doping density was obtained by calcination. The visible photocatalytic activity of Si-doped TiO2 NWs photoanode towards water splitting increased about three times as compared with pure TiO2 NWs. Reduction by H2S resulted in the enhanced electron transport and massive increase in charge-carrier density. This work provides a novel paradigm for silicon doping in materials for accelerating their carrier transport and applications.
关键词： Charge transport,Titanium dioxide,Silicon doping,Hydrothermal reaction,Water splitting
更新于2025-09-10 09:29:36
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Orbital Control of Long Range Transport in Conjugated and Metal-Centered Molecular Electronic Junctions
摘要： Large area molecular junctions consisting of covalently bonded molecular layers between conducting carbon electrodes were compared for Co and Ru complexes as well as nitroazobenzene and anthraquinone, in order to investigate the effect of molecular structure and orbital energies on electronic behavior. A wide range of molecular layer thickness (d) from 1.5-28 nm was examined, and revealed three distinct transport regimes in attenuation plots of current density (J) vs thickness. For d < 5 nm, the four molecular structures had comparable current densities and thickness dependence despite significant differences in orbital energies, consistent with coherent tunneling and strong electronic coupling between the molecules and contacts. For d > 12 nm, transport depends on electric field rather than bias, with the slope of ln J vs d near zero when plotted at constant electric field. At low temperature (T < 150 K), transport is nearly activationless and likely occurs by sequential tunneling and/or field induced ionization. For d =5-10 nm, transport correlates with the energy gap between the highest occupied and lowest unoccupied molecular orbitals, and ln J is linear with the square root of the bias or electric field. Such linearity occurs for all three transport regimes, and is consistent with energy barrier lowering by the applied electric field. The results clearly indicate a strong dependence of charge transport on molecular orbital energies provided d> 5 nm, with a variation of seven orders of magnitude of J for different molecules and d=10 nm. The results provide insights into charge transport mechanisms as well as a basis for rational design of molecular electronic devices.
关键词： molecular electronics,molecular junction,charge transport,multistep tunneling
更新于2025-09-10 09:29:36
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Charge transport in GaAs nanowires: Interplay between conductivity through the interior and surface conductivity
摘要： The charge transport through GaAs nanowires, partially p-doped and partially intrinsic, is analyzed by four-point resistance profiling along freestanding nanowires using a multip-STM. The charge transport channel in the undoped segment is assigned to the surface conductivity, while the interior of the nanowire is the conductance channel in the p-doped segment. The convoluted interplay between conduction through the interior of the nanowire and surface state conduction is studied in detail. Measurements of the I-V curves along the nanowires provide the experimental basis for the proposed charge transport model for the transition of the conduction from the interior to the surface of the nanowire. A voltage drop along the surface state conduction channel leads to an upward shift of the band edges at the surface. This results, for higher applied voltages, in the removal of the depletion layer and an opening of a conductance channel between the interior of the nanowire and the surface states.
关键词： GaAs nanowires,surface conductivity,multip-STM,charge transport,four-point resistance profiling
更新于2025-09-09 09:28:46
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Recent advances in bubble-assisted Liquid Hole-Multipliers in liquid xenon
摘要： We report on recent advances in the operation of bubble-assisted Liquid Hole-Multipliers (LHM). By con?ning a vapor bubble under or adjacent to a perforated electrode immersed in liquid xenon, we could record both radiation-induced ionization electrons and primary scintillation photons in the noble liquid. Four types of LHM electrodes were investigated: a THGEM, standard double-conical GEM, 50 μm-thick single-conical GEM (SC-GEM) and 125 μm-thick SC-GEM — all coated with CsI photocathodes. The 125 μm-thick SC-GEM provided the highest electroluminescence (EL) yields, up to ～ 400 photons per electron over 4π, with an RMS pulse-height resolution reaching 5.5% for events comprising ～ 7000 primary electrons. Applying a high transfer ?eld across the bubble, the EL yield was further increased by a factor of ～ 5. The feasibility of a vertical-mode LHM, with the bubble con?ned between two vertical electrodes, and the operation of a two-stage LHM con?guration were demonstrated for the ?rst time. We combine electrostatic simulations with observed signals to draw conclusions regarding the location of the liquid-gas interface and suggest an explanation for the observed di?erences in EL yield between the investigated electrodes.
关键词： Micropattern gaseous detectors (MSGC, GEM, THGEM, RETHGEM, MHSP, MICROPIC, MICROMEGAS, InGrid, etc),Noble liquid detectors (scintillation, ionization, double-phase),Charge transport, multiplication and electroluminescence in rare gases and liquids
更新于2025-09-09 09:28:46
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Deciphering the multifarious charge transport behaviour of crystalline propeller-shaped triphenylamine analogues
摘要： A collection of para-substituted propeller-shaped triphenylamine (TPA) derivatives have been computationally investigated for the charge transport characteristics exhibited by the derivatives using the Marcus-Hush formalism. The various substituents chosen in the current work, having features that range from electron withdrawing to electron donating nature, play a key role in defining the reorganization energy and electronic coupling properties of the TPA derivatives. TPA moiety is expected to possess weak electronic coupling on the basis of poor orbital overlap upon aggregation owing to the restriction imposed by the propeller shape of the triphenylamine core. However, the substituent groups attached to the TPA core can significantly dictate the crystal packing motif of the TPA derivatives, wherein the variety of noncovalent intermolecular interactions subsequently generated drive the packing arrangement and influence the electronic coupling between the neighbouring orbitals. The intermolecular interactions in the crystalline architecture of TPA derivatives were probed using Hirshfeld and QTAIM techniques. Furthermore, SAPT analysis of the TPA analogues has revealed that a periodic arrangement of energetically stable dimers having significant electronic coupling is essential in order to contribute a high charge carrier mobility to the overall crystal.
关键词： SAPT,Pi stacking,1-D charge transport pathway,Marcus-Hush formalism,Substituent effect
更新于2025-09-09 09:28:46
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Unraveling the Role of Multiphonon Excitations and Disorder Concerning the Meyer-Neldel Type Compensation Effect in Organic Semiconductors
摘要： The Meyer-Neldel (MN) compensation rule, implying an exponential increase in the prefactor with increasing activation energy in a thermally activated process, is naturally emerging in two-site transition rates as a result of multiphonon excitation processes. However, it has been recently demonstrated [Phys. Rev. B. 90, 245201 (2014)] that the experimentally observed compensation behavior for the temperature-activated charge transport in thin-film organic field-effect transistors (OFETs) is not a genuine phenomenon, but rather it is an apparent extrapolated effect that arises as a consequence of the partial filling of the Gaussian DOS distribution. To resolve the contradiction, we investigate the impact of different jump-rate models on macroscopic hopping-charge transport in a random organic system using an effective medium analytic approach. The principal result of this study is that the averaging over the individual jump rates in a conventional Gaussian disordered system erodes the genuine thermodynamically determined MN compensation effect, and therefore, the macroscopic transport no longer reflects the microscopic rates. The apparent compensation behavior observed for OFET mobilities upon varying the carrier concentrations can be reproduced regardless of the single-phonon or multiphonon character of activated transitions. Another remarkable finding is that the disorder formalism does predict a genuine MN compensation effect using multiphonon rates if a disordered semiconductor contains a significant concentration of deep traps, so that the cumulative DOS features a double-peak Gaussian. Thus, this study bridges the gap between Gaussian disorder and multi-excitation entropy (MEE) models concerning the MN effect, and has important implications for the interpretation of the isokinetic MN temperature in disordered organic semiconductors.
关键词： disorder,organic semiconductors,multiphonon excitations,charge transport,Meyer-Neldel rule
更新于2025-09-09 09:28:46
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A model for charge transport in semicrystalline polymer thin films
摘要： A model for simulating the charge transport properties of semicrystalline polymer (SCrP) using Monte Carlo simulation is reinvented. The model is validated by reproducing the experimentally observed ?eld and temperature dependence of mobility in Poly(3-hexylthiophene-2,5-diyl) (P3HT) thin ?lms. This study also provides a new physical insight to the origin of much debated negative ?eld dependence of mobility (NFDM) observed at low electric ?eld strengths in P3HT thin ?lms. The observed NFDM, which is not explainable with the mechanisms proposed earlier, is attributed to the weak dependence of transit time on the applied electric ?eld strengths. In the semicrystalline ?lms, the charge transport takes place mostly through the crystalline regions, in which the charge transport is weakly dependent on the strength of the applied electric ?eld. In addition, a possible explanation for the origin of Arrhenius temperature dependence of mobility (lnμ / 1/T) commonly observed in SCrP thin ?lms is also proposed.
关键词： Monte Carlo simulation,charge transport,poly(3-hexylthiophene-2,5-diyl),semicrystalline polymers,negative ?eld dependence of mobility
更新于2025-09-09 09:28:46
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Impact of Molecular Order on Polaron Formation in Conjugated Polymers
摘要： The nature of polaron formation has profound implications on the transport of charge carriers in conjugated polymers, but still remains poorly understood. Here we develop in situ electrochemical resonant Raman spectroscopy, a powerful structural probe that allows direct observation of polaron formation. We report that polaron formation in ordered poly(3-hexyl)thiophene (P3HT) polymer domains (crystalline phase) results in less pronounced changes in molecular conformation, indicating smaller lattice relaxation, compared to polarons generated in disordered polymer domains (amorphous phase) for which we observe large molecular conformational changes. These conformational changes are directly related to the effective conjugation length of the polymer. Furthermore, we elucidate how blending the P3HT polymer with phenyl C-61 butyric acid methyl ester (PCBM) affects polaron formation in the polymer. We find that blending disturbs polymer crystallinity, reducing the density of polarons that can form upon charge injection at the same potential, whilst the lost capacity is partly restored during post-deposition thermal annealing. Our study provides direct spectroscopic evidence for a lower degree of lattice reorganisation in crystalline (and therefore more planarised) polymers than in conformationally disordered polymers. This observation is consistent with higher charge carrier mobility and better device performance commonly found in crystalline polymer materials.
关键词： electrochemical resonant Raman spectroscopy,conjugated polymers,polaron formation,molecular order,PCBM,charge transport,P3HT
更新于2025-09-09 09:28:46
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Ambipolar charge transport in an organic/inorganic van der Waals p–n heterojunction
摘要： Hybrid two-dimensional (2D) van der Waals (vdW) p–n junctions are attractive due to the controlled synthesis of the physical performances of organic semiconductors and quantum confinement effects of 2D materials, enabling highly tunable optoelectronic performances as well as low-cost processability. Here, hybrid 2D heterostructures are fabricated using a p-type semiconducting polymer (PDVT-10) and n-type MoS2. An ultra-thin film (B9 nm) of the PDVT-10 polymer is formed using the Langmuir–Schaefer (LS) technique. Large-scale MoS2 monolayers are prepared using a chemical vapor deposition (CVD) method. The PDVT-10/MoS2 vertical heterojunction devices show ambipolar charge transport properties with a p-type maximum field-effect mobility of 0.3 cm2 V(cid:2)1 s(cid:2)1 and an n-type maximum field-effect mobility of 2.45 cm2 V(cid:2)1 s(cid:2)1. In addition, the heterojunctions exhibit a great photoresponse under white light as well as a clear rectifying behavior.
关键词： PDVT-10,p–n heterojunction,organic/inorganic,van der Waals,ambipolar charge transport,MoS2
更新于2025-09-09 09:28:46