Cu2O/Cu/TiO2 nanotube Ohmic heterojunction arrays with enhanced photocatalytic hydrogen production activity

Cu₂O/Cu/TiO₂ nanotube heterojunction arrays were prepared by assembling Cu@Cu₂O core-shell nanoparticles on TiO₂ nanotube arrays (NTAs) using a facile impregnation-reduction method. SEM and TEM results show that Cu@Cu₂O plate-like nanoparticles with tens of nanometers in size are confined inside TiO₂ NTAs. Only the outmost several nanometers of the nanoparticles are Cu₂O and the predominant inner of the nanoparticles are Cu metals. Cu L₃VV Auger spectra of Cu₂O/Cu/TiO₂ NTAs suggest that Cu metals are enveloped by at least several nanometers Cu₂O on the surface, which further confirms the Cu@Cu₂O core shell structure of Cu nanoparticles. The ability of light absorption of Cu₂O/Cu/TiO₂ NTAs is enhanced. The range of absorption wavelengths changes from 400 to 700 nm due to the surface plasmon response of Cu metals core and Cu₂O nanoparticles shell. The photocatalytic hydrogen production rate of Cu₂O/Cu/TiO₂ heterojunction arrays is enhanced when compared with those of Cu₂O/TiO₂ NTAs and TiO₂ NTAs under UV light. Moreover, a stable H₂ generation property was obtained under visible light (λ gt; 400 nm). The Cu metal core is believed to play a key role in the enhancement of photocatalytic properties of Cu₂O/Cu/TiO₂ nanotube heterojunction arrays.     

Properties of PEDOT:PEG/ZnO/p-Si heterojunction diode

The zinc oxide (ZnO) and poly(3,4-ethylenedioxythiophene) bis-poly(ethyleneglycol) (PEDOT:PEG) films were deposited on p-Si substrate by sputter and spin coating methods, respectively. An organic/inorganic heterojunction diode having PEDOT:PEG/ZnO on p-Si substrate was fabricated. The barrier height (BH) and the ideality factor values for the device were found to be 0.82 ± 0.01 eV and 1.9 ± 0.01, respectively. It has been seen that the value of BH is significantly larger than those of conventional Au/p-Si metal–semiconductor contacts. The PEDOT:PEG/ZnO/p-Si heterostructure exhibits a non-ideal I–V behavior with the ideality factor greater than unity that could be ascribed to the interfacial layer, interface states and series resistance. The modified Norde's function combined with conventional forward I–V method was used to extract the parameters including the barrier height and series resistance. At the same time, the physical properties of ZnO and PEDOT:PEG films deposited by sputter and spin coating technique, respectively, were investigated at room temperature. The obtained results indicate that the electrical parameters of the diode are affected by structural properties of ZnO film and PEDOT:PEG organic film.     

p型微晶硅膜的研究及其在异质结太阳电池中的应用

首先采用射频等离子体增强化学气相沉积技术制备了电导率为0.13 S/cm、晶化率为50%的p型微晶硅,然后制备了μc-Si∶H(p)/c-Si(n)异质结太阳电池。初步研究了硼掺杂比、辉光功率密度、p型硅薄膜的厚度和氢处理时间等这些参数对电池开压的影响。在优化的工艺参数下得到异质结电池最大开路电压Voc为564mV。     

Photovoltaic properties of SnS based solar cells

Polycrystalline thin films of tin sulphide have been synthesised using spray pyrolysis. The layers grown at a temperature of 350 °C had the orthorhombic crystal structure with a strong (1 1 1) preferred orientation. The films had resistivities 30 Ω cm with an optical energy band gap (E_g) of 1.32 eV. Heterojunction solar cells were fabricated using sprayed SnS as the absorber layer and indium doped cadmium sulphide as the window layer and the devices were characterised to evaluate the junction properties as well as the solar cell performance. The current transport across the junction has been modelled as a combination of tunnelling and recombination. The best devices had solar conversion efficiencies of 1.3% with a quantum efficiency of 70%.     

Fluorine doped indium oxide films for silicon solar cells

The effect of conditions of preparation of the In₂O₃:F(IFO)/(pp⁺)Si solar cell (SC) by pyrosol method was systematically studied with the goal to maximize its photovoltage. Heterojunction IFO/(pp⁺)Si SC was obtained with the efficiency of 16.6% and photovoltage of 617 mV as well as the IFO/(n⁺pp⁺)Si SC with the efficiency of 19.2% using the following obtained optimal conditions: film-forming solution: 0.2 M InCl₃ + 0.05 M NH₄F + 0.1 M H₂O in methanol; carrier gas — Ar + 5% O₂; deposition temperature — 480 °C; duration of deposition — 2 min; two-minute annealing in argon with sprayed methanol at a temperature of 380 °C.     

Low-base-resistance InP/InGaAs heterojunction bipolar transistors with a compositionally graded-base structure

To reduce base resistance of an InP/InGaAs heterojunction bipolar transistor grown by gas-source molecular beam epitaxy, the doping characteristics of carbon-doped InGaAs and the dependence of doping concentration on current gain were investigated. Using a thicker graded base was found to increase current gain significantly, resulting in increased doping level in the InGaAs: C-base layer. In particular, an 80-nm-thick graded base produces a base sheet resistance of 285 Ω/sq and maintains a practically useful current gain of 23 and a high cut-off frequency of 139 GHz.     

Solution p-doped fluorescent polymers for enhanced charge transport of hybrid organic-silicon nanowire photovoltaics

The solution p-type doping of various conjugated polymers and small molecules via blending with tetrafluorotetracyano-quinodimethane (F4-TCNQ) is investigated to facilitate hole transport for hybrid organic-silicon-nanowire solar cells. Among all, the highly-fluorescent conjugated polymers such as poly(9,9-dioctylfluorenyl-2,7-diyl) (PFO) demonstrate superior transport characteristics, where both the device fill-factor and power conversion efficiency (PCE) are positively correlated with the doping concentration. The best PCE achieves 13.66% from the device with 30% p-doped PFO, compared to the reference at 12.50%. The enhancement is ascribed to the efficient interfacial charge-carrier recombination with minimal energy losses. A vertically graded doping profile is further revealed with F4-TCNQ molecules preferentially accumulated near the silicon surface.     

Facile synthesis of defected TiO2-x (B) nanosheet/graphene oxide hybrids with high photocatalytic activity

TiO2 (B) nanosheets/GO (graphene oxide) hybrids are considered to be outstanding performance pho-tocatalysts for high efficiency of H2 evolution.However,they still suffer severe challenges during the synthetic processes,such as a large amount of the capping agents adhering on the surface and easy occurrence of aggregation.To figure out these obstacles,Ar plasma treatment as a modified method in this study not only enable the TiO2 (B) nanosheets distributed uniformly on the GO sheets but also engi-neer defects within TiO2 (B) nanosheetsto significantly improve the photocatalytic activity for the water splitting.The hydrogen evolution rate of the TiO2-x (B)/GO sheets is 1.4 times higher compared with that of original TiO2 (B)/GO sheets without Ar plasma treatment.The improved photocatalytic proper-ties were owing to the synergetic effects of oxygen vacancies and the heterojunction between GO and TiO2 (B),which can promote the visible light utilization and accelerate separation and transportation of photogenerated electron-holes.This study can provide a facile pathway to prepare the two-dimensional hybrid photocatalysts with high photocatalytic H2 activity.     

Large-area (64 × 64 array) inkjet-printed high-performance metal oxide bilayer heterojunction thin film transistors and n-metal-oxide-semiconductor (NMOS) inverters

It is a big challenge to construct large-scale,high-resolution and high-performance inkjet-printed metal oxide thin film transistor (TFT) arrays with independent gates for the new printed displays.Here,a self-confined inkjet printing technology has been developed to construct large-area (64 × 64 array),high-resolution and high-performance metal oxide bilayer (In2O3/IGZO) heterojunctionTFTs with independent bottom gates on transparent glass substrates.Inkjet printing In2O3 dot arrays with the diameters from 55 to 70 μm and the thickness of ～10 nm were firstly deposited on UV/ozone treated AIOx dielectric layers,and then IGZO dots were selectively printed on the top of In2O3 dots by self-confined technology to form In2O3/IGZO heterojunction channels.When the inkjet-printed IO layers treated by UV/ozone for more than 30 min or oxygen plasma for 5 min prior to print IGZO thin films,the mobility of the resulting printed In2O3/IGZO heterojunction TFTs are correspondingly enhanced to be 18.80 and 28.44 cm2 V-1 s-1 with excellent on/off ratios (＞108) and negligible hysteresis.Furthermore,the printed N-Metal-Oxide-Semiconductor (NMOS) inverter consisted of an In2O3/IGZO TFT and an IGZO TFT has been demonstrated,which show excellent performance with the voltage gain up to 112.The strategy demonstrated here can be considered as general approaches to realize a new generation of high-performance printed logic gates,circuits and display driving circuits.     

Fly ash cenospheres as multifunctional supports of g-C3N4/N-TiO2 with enhanced visible-light photocatalytic activity and adsorption

The ternary composites of g-C₃N₄/N-TiO₂/FACs (FAC: Fly Ash Cenospheres) were synthesized by an in-situ hydrolysis method to improve the photocatalytic activity and their stability. When TiO₂ was anchored on FAC, it was easily to be separated from the aqueous solution and could be repeatedly utilized. In the present experiments, the degradation rate remained for more than 68% even after the composite reused for seven times. The band gap of g-C₃N₄/N-TiO₂/FAC was 2.75?eV, which might be owing to the synergistic effect between N-TiO₂ and g-C₃N₄. The composite of g-C₃N₄/N-TiO₂/FAC had an ideal activity of 72.2% under visible light illumination for 180?min. It was about 1.3 times of N-TiO₂/FAC and 3.5 times of g-C₃N₄. The synergistic effect of SiO₂, Fe₂O₃ and TiO₂ components resulted to the improvement of photocatalytic performance.