In this study, the influence on the surface passivation properties of crystalline silicon according to silicon wafer thickness, and the correlation with a-Si:H/c-Si heterojunction solar cell performances were investigated. The wafers passivated by p(n)-doped a-Si:H layers show poor passivation properties because of the doping elements, such as boron(B) and phosphorous(P), which result in a low minority carrier lifetime (MCLT). A decrease in open circuit voltage (Voc) was observed when the wafer thickness was thinned from 170μm to 50μm. On the other hand, wafers incorporating intrinsic (i) a-Si:H as a passivation layer showed high quality passivation of a-Si:H/c-Si. The implied Voc of the ITO/p a-Si:H/i a-Si:H/n c-Si wafer/i a-Si:H/n a-Si:H/ITO stacked layers was 0.715 V for 50μm c-Si substrate, and 0.704 V for 170μm c-Si. The Voc in the heterojunction solar cells increased with decreases in the substrate thickness. The high quality passivation property on the c-Si led to an increasing of Voc in the thinner wafer. Short circuit current decreased as the substrate became thinner because of the low optical absorption for long wavelength light. In this paper, we show that high quality passivation of c-Si plays a role in heterojunction solar cells and is important in the development of thinner wafer technology.

The a-Si:H/c-Si hetero-junction (HJ) solar cells have a variety of advantages in efficiency and fabrication processes. It has already demonstrated about 23% in R&D scale and more than 20% in commercial production. In order to further reduce the fabrication cost of HJ solar cells, fabrication processes should be simplified more than conventional methods which accompany separate processes of front and rear sides of the cells. In this study, we propose a simultaneous deposition of intrinsic thin a-Si:H layers on both sides of a wafer by dual hot wire CVD (HWVCD). In this system, wafers are located between tantalum wires, and a-Si:H layers are simultaneously deposited on both sides of the wafer. By using this scheme, we can reduce the process steps and time and improve the efficiency of HJ solar cells by removing surface contamination of the wafers. We achieved about 16% efficiency in HJ solar cells incorporating intrinsic a-Si:H buffers by dual HWCVD and p/n layers by PECVD.

Silicon heterojunction solar cells have been studied by many research groups. In this work, silicon heterojunction solar cells having a simple structure of Ag/ZnO:Al/n type a-Si:H/p type c-Si/Al were fabricated. Samples were fabricated to investigate the effect of transparent conductive oxide growth conditions on the interface between ZnO:Al layer and a-Si:H layer. One sample was deposited by ZnO:Al at low working pressure. The other sample was deposited by ZnO:Al at alternating high working pressure and low working pressure. Electrical properties and chemical properties were investigated by light I-V characteristics and AES method, respectively. The light I-V characteristics showed better efficiency on sample deposited by ZnO:Al by alternating high working pressure and low working pressure. Atomic concentrations and relative oxidation states of Si, O, and Zn were analyzed by AES method. For poor efficiency samples, Si was diffused into ZnO:Al layer and O was diffused at the interface of ZnO:Al and Si. Differentiated O KLL spectra, Zn LMM spectra, and Si KLL spectra were used for interface reaction and oxidation state. According to AES spectra, sample deposited by high working pressure was effective at reducing the interface reaction and the Si diffusion. Consequently, the efficiency was improved by suppressing the SiOx formation at the interface.

This paper investigates the dependence of a-Si:H/c-Si passivation and heterojunction solar cell performances on various cleaning processes of silicon wafers. It is observed that the passivation quality of a-Si:H thin-films on c-Si wafers depends highly on the initial H-termination properties of the wafer surface. The effective minority carrier lifetime (MCLT) of highly H-terminated wafer is beneficial for obtaining high quality passivation of a-Si:H/c-Si. The wafers passivated by p(n)-doped a-Si:H layers have low MCLT regardless of the initial H-termination quality. On the other hand, the MCLT of wafers incorporating intrinsic (i) a-Si:H as a passivation layer shows sensitive variation with initial cleaning and H-termination schemes. By applying the improved cleaning processes, we can obtain an MCLT of 100μsec after H-termination and above 600μsec after i a-Si:H thin film deposition. By adapting improved cleaning processes and by improving passivation and doped layers, we can fabricate a-Si:H/c-Si heterojunction solar cells with an active area conversion efficiency of 18.42%, which cells have an open circuit voltage of 0.670V, short circuit current of 37.31 mA/cm2 and fill factor of 0.7374. These cells show more than 20% pseudo efficiency measured by Suns-Voc with an elimination of series resistance.

Cinnamyl alcohol dehydrogenase (CAD, EC 1.1.1.95), catalyzes the reduction of hydroxycinnamaldehydes to give hydroxycinnamyl alcohols, or "monolignols," the monomeric precursors of lignin. Lignins are important components of cell walls and lignified secondary cell walls play crucial roles in long distance transport of water and nutrients during plant growth and development and in plant defense against biotic and abiotic stresses. Here a cDNA clone containing a CAD gene, named as PgCAD, was isolated from a commercial medicinal plant Panax ginseng. PgCAD is predicted to encode a precursor protein of 177 amino acid residues, and its sequence shares high homology with a number of other plant CADS. The expression of PgCAD in adventitious roots and hairy roots of P. ginseng was analyzed using reverse transcriptase (RT)-PCR under various abiotic stresses such as salt, salicylic acid, wounding and chilling treatment that triggered a significant induction of PgCAD at different time points within 2-48 h post-treatment. This study revealed that PgCAD may help the plants to survive against various abiotic stresses.

Malate dehydrogenase is a ubiquitous enzyme in plants, involving in a range of metabolic processes depending on its subcellular location. A malate dehydrogenase (PgMDH) cDNA was isolated and characterized from the root of Panax ginseng C. A. Meyer. The deduced amino acid sequence of PgMDH showed high similarity with the NAD-dependent mitochondrial malate dehydrogenase from Glycinemax (P17783), Eucalyptus gunnii (P46487), and Lycopersicon esculentum (AAU29198). And the segment of a malate dehydrogenase gene was amplified through RT-PCR. The expression of PgMDH was increased after treatments of chilling, salt, UV, cadmium or copper treatment.

인삼의 생장에서 염류의 집적은 우량 인삼의 생산에 많은 장애요인이 되고 있다. 본 연구에서는 순계 분리된 인삼의 우수 계통으로부터 NaCl 처리에 따른 생장율 조사와 ginsenoside의 생산에 미치는 영향을 조사하였다. 선발된 모상근(KGHR-8)으로부터 ginsenosides의 함량에 미치는 NaCl의 최적 농도를 조사하기 위하여 30일간 배양한 결과 NaCl의 농도가 증가함에 따라 모상근의 생장은 감소하였지만, total ginsenoside의 함량은 0.24M NaCl 처리구에서 높은 증가를 가져왔으며 특히 광을 조사하여 배양한 결과 높게 검출되었다. 0.24 M NaCl 농도로 광상태하에서 함량은 61.7% 증가하는 양상을 나타내었다. (Table 1). 또한 모상근의 생장을 최적 상태로 설정하기 위해 two step culture 방법을 조사한 결과, 0.05M, 0.1M NaCl 처리시 모상근의 생장율은 각각 약 62%, 76% 감소한 반면, ginsenoside의 함량은 29%, 48% 각각 향상되었다. 모상근은 방어기작의 일환으로 NaCl을 elicitor로 인지하고 2차대사산물인 사포닌의 생산에 영향을 미치는 것으로 확인되었다.

The purpose of this study was to evaluate the partial oxidation of the biological treatment plant effluents using Fenton`s reagent as a pretreatment step prior to a tertiary biological oxidation of these effluents. Fenton`s reagent was evaluated as a pretreatment process for inhibitory or refractory organics. Based on the Fenton oxidation system, the petrochemical wastewater treatment plant effluent was shown to have significant improvement in toxicity after oxidation with hydrogen peroxide. For example, at range of 42∼184 ㎎/L COD of petrochemical plant effluents, the COD removal efficiencies were from 38.2% to 60.1% after reaction with hydrogen peroxide 200 ㎎/L and Fe^2+ 100 ㎎/L and reaction time was 30 minutes. The total TOC reduction were about 15.8∼22.4% with same test condition and difference between the overall removal rate and BOD/COD ratio after Fenton`s oxidation estabilished in the biodegradation and otherwise meets the discharge standard or reuse for cooling tower make-up water.