构建MoS2/Fe-g-C3N4异质结催化剂以促进其可见光催化产氢性能

以g-C_3N_4为基底,通过掺杂Fe元素,复合MoS_2的方法制备了具有多孔异质结结构的MoS_2/Fe-g-C_3N_4半导体材料,并测量了其光解水产氢性能,发现MoS_2含量为3%(以g-C_3N_4的质量为基准,下同)时,MoS_2/Fe-g-C_3N_4的光催化性能优异,其产氢速率达到48.2μmol/h,为g-C_3N_4的5.48倍。利用XRD、FTIR、SEM、TEM、XPS表征了催化剂的物化性质;利用PL、UV-Vis等方法表征了催化剂的光学性质。结果发现,Fe元素的掺杂使g-C_3N_4结晶度降低,并呈现一种交叉孔道结构,极大增加了催化剂的比表面积。同时,MoS_2可以与g-C_3N_4形成异质结结构,提高了MoS_2/Fe-g-C_3N_4的可见光吸收率以及光生电子-空穴对的分离效率,从而有效提高了MoS_2/Fe-g-C_3N_4光解水产氢的能力。     

Double-polysilicon SiGe HBT architecture with lateral base link

We present an analysis of a modified double-polysilicon SiGe:C HBT module showing a CML ring oscillator gate delay τ_D of 2.5 ps, and f_T/f_max/BV_CEo values of 300 GHz/350 GHz/1.85 V (Fox et al., 2008) [1]. A key feature of the HBT module is a connection of the extrinsic and intrinsic base regions by lateral epitaxial overgrowth, which aims to overcome the limits of the conventional double-polysilicon architecture in simultaneously reducing R_B and C_BC. Potential benefits and barriers of the proposed device structure on the way to higher performance are reviewed with regard to the recently demonstrated performance gain of the classical double-polysilicon approach. The paper addresses technological challenges one is faced when the here presented device structure is scaled to minimum device dimensions.     

Revisiting the electronic properties of Molecular Semiconductor – Doped Insulator (MSDI) heterojunctions through impedance and chemosensing studies

The core activity of this work was to give a new interpretation of the electronic behavior of Molecular Semiconductor – Doped Insulator heterojunctions (MSDI), a new organic device combining two molecular materials with very different electronic properties. We focused on understanding the phenomenon occurring at the interface of fluorinated and non-fluorinated phthalocyanines that appears to be a determining factor for the electronic charge transport in the two-component thin film and ultimately deciding the nature of gas sensing, as illustrated with ozone and ammonia chosen as examples of accepting and donating gases. The impedance measurements showed that the Schottky contact between the sublayer and the electrodes also plays a key role. They, furthermore, provide complementary data for the selective detection of ammonia and relative humidity in air.     

A photovoltaic cell from p-type boron-doped amorphous carbon film

Boron-doped amorphous carbon (a-C(B)) films were prepared on n-type silicon using pulsed laser deposition technique of a graphite target. The a-C(B) films have been proved to be p-type by the formation of a heterojunction between the a-C(B) film and n-Si. The device of a-C(B)/n-Si structure yielded an open-circuit voltage (V_oc) of 0.27 V and a short-circuit current density (J_sc) of 2.2 mA/cm² under illumination (AM1.5 100 mW/cm²). According to calculation, the energy conversion efficiency and fill factor were found to be about 0.3% and 0.53, respectively.     

Photoluminesence studies of CdTe/SnO2 and CdTe/CdS heterojunctions: The influence of oxygen and the CdCl2 heat treatment

The influence of oxygen and annealing in the presence of CdCl₂ on the photoluminescence (PL) spectra of CdTe, component of SnO₂/CdTe heterojunction (HJ), has been studied in a temperature range of 17-100 K. The changes in the photoluminescence spectra were studied as a function of excitation intensity. Analysis of the PL spectra was carried out with considerations of spectra obtained from CdS/CdTe heterojunctions. CdTe side PL (SnO₂/CdTe HJ) consisted of 1.450 eV-DA defect band and 1.243 eV band (17 K). Annealing resulted in the disappearance of 1.243 eV band in oxygen containing samples. Interface PL for the unannealed samples consisted of mainly the 1.264 eV and a trace of the defect band. The CdCl₂ treatment is responsible for an almost symmetrical 1.416 eV band.     

Amorphous silicon carbide heterojunction solar cells on p-type substrates

The performance of silicon heterojunction (SHJ) solar cells is discussed in this paper in regard to their dependence on the applied amorphous silicon layers, their thicknesses and surface morphology. The emitter system investigated in this work consists of an n-doped, hydrogenized, amorphous silicon carbide a-SiC:H(n) layer with or without a pure, hydrogenized, intrinsic, amorphous silicon a-Si:H(i) intermediate layer. All solar cells were fabricated on p-type FZ-silicon and feature a high-efficiency backside consisting of a SiO₂ passivation layer and a diffused local boron back surface field, allowing us to focus only on the effects of the front side emitter system. The highest solar cell efficiency achieved within this work is 18.5%, which is one of the highest values for SHJ-solar cells using p-type substrates. A dependence of the passivation quality on the surface morphology was only observed for solar cells including an a-Si:H(i) layer. It could be shown that the fill factor suffers from a reduction due to a reduced pseudo fill factor for emitter thicknesses below 11 nm due to a lower passivation quality and/or a higher potential for shunting thorough the a-Si emitter to the crystalline wafer with the conductive indium tin oxide layer. Furthermore, the influence of a variation of the doping gas flow (PH₃) during the plasma enhanced chemical vapor deposition of the doped amorphous silicon carbide a-SiC:H(n) on the solar cell current-voltage characteristic-parameter has been investigated. We could demonstrate that a-SiC:H(n) shows in principle the same dependence on PH₃-flow as pure a-Si:H(n).     

Fabrication of p-type CuSCN/n-type micro-structured ZnO heterojunction structures

Micro-sized ZnO rods on a SnO₂ coated glass substrate were obtained by the spray pyrolysis method. Then a p-type CuSCN layer was deposited on this micro-sized n-ZnO to produce a p-n heterojunction. Temperature dependent current-voltage characteristics were measured in the temperature range 150-300 K with a step of 25 K. The current-voltage characteristics exhibit electrical rectification behavior. The zero bias barrier height Φ_b0 increases and the ideality factor n decreases with an increase in temperature. The apparent Richardson constant and mean barrier height were found to be 0.0028 A cm^− 2 K^− 2 and 0.228 eV respectively in the range 150-300 K. After a barrier height inhomogeneity correction, the Richardson constant and the mean barrier height were obtained as 65.20 A cm^− 2 K^− 2 and 0.840 eV, respectively.     

Junction formation in chalcopyrite solar cells by sputtered wide gap compound semiconductors

In an effort to eliminate the CdS buffer layer and its costly preparation process we are considering sputtered buffer layers. In particular, we report in this contribution on the reactive sputtering of wide gap Zn(O,S) compound semiconductors and their application in solar cells with different types of chalcopyrite absorbers. While we were able to freely adjust the composition through the oxygen partial pressure, the structural and optical properties are superior when the composition is close to the ternary endpoints. Open circuit voltage and short circuit current density as a function of Sulphur content in the buffer show opposite trends. Working cells were achieved with low band gap as well as wide band gap absorbers, however, their performance is so far inferior to that of the standard stacks.     

A technological evolution from bulk crystalline age to multilayers thin film age in solar photovoltaics

Recent advances in solar cell device technologies are surveyed, and a new trend underlying is predicted by a term “technological evolution from the bulk crystalline age to the multilayered thin film age”. In the paper, firstly, recent progress of thin film fabrication technologies for active materials of photovoltaic device are reviewed, and their significancies such as wide area, low temperature growth etc., are pointed out from currently developed live technologies. Secondly, some R & D efforts to develop the next generation type solar cells utilized by full use of multi-layers thin film growth technology are introduced together with some newly developed integrated process technology for the thin film solar cells. Then, some topics in the high cost performance multi-layers thin film solar cells are also introduced. In the final part of this paper, the current state of the art in the field of thin film solar cells and their industrialization are overviewed and the market expansion toward the 21st century is forecast, and discussed.