Ultra-high quality surface passivation of crystalline silicon wafers in large area parallel plate reactor at 40 MHz

We use a new in-house, large area and automated deposition system: the usable deposition area is 410 × 520 mm with RF-frequency of 40 MHz. We deposit intrinsic a-Si:H layer on flat p-type or n-type c-Si wafers after performing an HF dip. The overall recombination of these double-side passivated c-Si wafers is measured with an effective lifetime measurement set-up. We pay particular attention to the uniformity of the passivation obtained on the whole deposition area.We point out a major role of hydrogen dilution on quality of c-Si passivation. Excellent uniformity is obtained on the whole area with implied open-circuit voltages (V_oc) in a ± 1.5% range. We achieve excellent passivation with overall lifetimes approaching 7 ms (at Δn ≈ 4.5·10¹⁴ cm^− 3) resulting in implied V_oc of 708 mV on p-type c-Si; and lifetimes superior to 4.7 ms resulting in implied V_oc of 726 mV on n-type c-Si (S_eff less than 2 cm/s for both). These results open the way to very high efficiency heterojunction solar cell fabrication in large area reactors.     

An a-Si:H/SiGe/Si punchthrough heterojunction phototransistors with an thin-Al film

An a-Si:H/SiGe/Si punchthrough heterojunction phototransistors (PTHPTs), responding to a wavelength of 850 nm, have been proposed and demonstrated in this work. The dramatic difference between PTHPTs and conventional heterojunction phototransistors is that the base is completely depleted in the PTHPTs, thus a larger optical gain is achieved due to the lack of a neutral base. Furthermore, the use of low-temperature a-Si:H instead of conventional crystalline silicon, a strained SiGe can be preserved at the interface of base and emitter, allowing ultrashallow junctions and abrupt doping profiles. Another advantage is that the a-Si:H can provide large valence-band discontinuity between base and emitter, avoiding photogenerated holes injected from base to emitter, and hence a larger collector current. In addition, we employed a thin Al-coating covered on the surface of emitter to enhance the collection of photogenerated holes. In comparison to the PTHPTS without the thin-Al coating, the optical gain of PTHPTs with thin-Al coating is increased from 922 to 3970 at 5-V bias voltage, responding to a light source of 850 nm with 0.028 mW.     

可见光LED的进展——超高亮度LED及应用(二)

可见光ＬＥＤ的进展——超高亮度ＬＥＤ及应用（二）张万生梁春广（电子工业部第十三研究所，石家庄，０５００５１）４超高亮度发光管的发展［９～１４］４．１ＩｎＧａＡｌＰＤＨＬＥＤ发光强度达到坎德拉级发光管的高亮度化一直是半导体材料和器件的前沿课题之一，超高...     

a-Si:H/CuInS2 heterojunctions for photovoltaic conversion

Heterojunctions of hydrogenated a-Si films prepared by r.f. sputtering with spraypyrolyzed CuInS₂ films have been studied. Capacitance-voltage measurements establish the formation of abrupt heterojunction. The barrier height varies from 0·26 to 0·55 V as the resistivity of CuInS₂ film decrease from 1·5 × 10³ to 65 Θm. These junctions exhibit photovoltaic behaviour withV _oc = 220 mV andI _sc = 0·20 mA/cm².     

Fabrication of a Cu2-xSe/rGO heterojunction photocatalyst to achieve efficient photocatalytic H2 generation

The present study has successfully fabricated a Cu_2-xSe/rGO heterojunction for the first time using an in situ hot-injection method and employed it to produce photocatalytic hydrogen. The optimal Cu_2-xSe/3%rGO can achieve an efficient photocatalytic H₂ production at the rate 3123.48 μmol g⁻¹ h⁻¹, nearly 3.46 times higher than that of the pure Cu_2-xSe. The enhanced activity can be attributed to facilitated light absorption, up-regulated charge density, lower interfacial transfer resistance as well as a longer electron decay lifetime. In the meantime, the expanded specific surface area can create more active reaction sites, leading to the enhancement of photocatalytic peropeties. Besides, the mechanism of the Cu_2-xSe/rGO heterojunction's hydrogen production is proposed.     

Molybdenum doping effects for bismuth vanadate photocatalysts on electrochemical performances using the solution process

Metal-doping is widely used to enhance charge generation and reduce carrier recombination of BiVO₄ for catalyzing water oxidation. In this work, different Mo-doping levels are applied to synthesize Mo-doped BiVO₄ (MBVO) on conductive glasses. Molybdenum plays multiple roles of dopant, structure-confined mediator, and sources for forming additional semiconductor. The MBVO with lower Mo-doping levels presents bi-layered structure with nanowire overlayer and nanorod underlayer, which can develop facile one-dimensional charge-transfer paths and efficient heterojunction. With preferable design of nanowire and nanorod layers, the high light absorption, small charge-transfer resistance and high carrier density are attained for MBVO with 1% Mo-doping, which shows the highest photocurrent density of 2.5 mA/cm² at 1.23 V_RHE, smallest onset potential of 0.22 V_RHE and highest maximum photoconversion efficiency of 2.20%. This work carefully illustrates the function of molybdenum and firstly constructs the unique bi-layered structure for MBVO to display outstanding photoelectrochemical performance for catalyzing water oxidation.     

Ar plasma treatment on ZnO–SnO2 heterojunction nanofibers and its enhancement mechanism of hydrogen gas sensing

In this study, ZnO–SnO₂ heterojunction nanofibers were fabricated using electrospinning and treated by Ar plasma. The post treatment demonstrated the ability to regulate adsorbed oxygen of nanofibers and thus affecting the gas sensing performance. The results revealed that the gas sensing performances increased with the increase of plasma treatment time at first, then showed a downward trend. The setting for the best H₂ gas performance was 20 min of plasma treatment, under which the response of the sample was 80% higher and the response time was two thirds shorter than those of the untreated sample. The explanation can be that appropriate plasma treatment can increase the oxygen vacancy on the surface of heterojunction nanofibers as well as the resistance modulation range in the air; however, excessive plasma treatment can result in the reduction of the resistance modulation range in the air by reducing the metal oxide to metal.     

Fabrication of WO3 based nanocomposites for the excellent photocatalytic energy production under visible light irradiation

Energy crisis and higher demands have lead scientists to search for economic and reliable sources of energy. In this research work, WO₃/BiVO₄ (1%,2%,3% and 4%) composites are synthesized by using a facile hydrothermal method to produce hydrogen energy from biomass through photoelectrochemical cells. The photoanodes were made by using spin coating methods. The experimental results were analyzed by the SEM, XRD, UV–Vis, PL, and BET spectroscopic techniques. The XRD results showed that the material is crystalline and the average crystallite size is in the range of 50–55 nm, the SEM results showed that the materials have spheres-like nanostructures. The UV and PL results exhibited that absorption region increased and recombination rate decreased by adding BiVO₄ up to 3%. The BET results showed the porosity of the material and exhibited that WO₃/BiVO₄ (3%) has a large surface area (m²/g). The efficiency was analyzed by producing hydrogen energy and the results revealed that WO₃/BiVO4 (3%) showed the highest efficiency for producing hydrogen energy, which is 330.9 micro-mol.h⁻¹.g⁻¹. The material also showed excellent stability even after the third cycle. The extraneous efficiency caused due to redshift of the WO₃/BiVO₄(3%), high redox potential, high crystallinity, small bandgap and electronic interaction across the electrodes for the production of hydrogen gas fuel during efficient photocatalytic activity. Moreover, WO₃/BiVO₄ (3%) is proved to be an active and favourable photocatalyst for the production of hydrogen energy from biomass/bio-wastes, which can be further utilized in various energy applications.     

Constructing rod-shaped Co2C/MoN as efficient bifunctional electrocatalyst towards overall urea-water electrolysis

In this paper, Co₂C/MoN/NF at different calcination temperatures (T = 500, 550, 600, 650, 700 °C) was prepared in situ on 3D foam nickel (NF) by hydrothermal treatment and high-temperature calcination. The experimental results show that the sample synthesized at 600 °C (Co₂C/MoN-600/NF) has the best catalytic capacity and the maximum electrochemical active area. For the hydrogen evolution reaction (HER), the potential is only ?176 mV at 100 mA cm^?2, meanwhile, only 1.42 V is needed for urea oxidation reaction (UOR). Furthermore, a two-electrode electrolyze cell of Co₂C/MoN-600/NF6Co₂C/MoN-600/NF was constructed. And the voltage required for overall urea splitting (OUS) is 1.507 V at 50 mA cm^?2, which is 171 mV lower than that of overall water splitting (OWS, 1.678 V). Moreover, the prepared catalyst not only can treat urea in wastewater but also catalyze the production of hydrogen. Therefore, it will be a promising green electrocatalyst.