1,1′‐Di(hydrazinocarbonylmethyl)‐2,2′‐biimidazole monohydrate and 1,1′‐di[2‐(hydrazinocarbonyl)ethyl]‐2,2′‐bi­imidazole

The crystal structures of the title compounds, alternatively called 2,2′‐(2,2′‐bi­imid­azole‐1,1′‐diyl)­diaceto­hydra­zide monohydrate, C₁₀H₁₄N₈O₂·H₂O, (I), and 3,3′‐(2,2′‐bi­imid­azole‐1,1′‐diyl)­dipropion­o­hydra­zide, C₁₂H₁₈N₈O₂, (II), respectively, have been determined. The mol­ecules consist of half‐mol­ecule asymmetric units related by a twofold rotation in (I) and by a center of inversion in (II). The imidazole rings of both mol­ecules crystallize in a nearly coplanar fashion [dihedral angles of 5.91 (3) and 0.0 (1)° for (I) and (II), respectively]. Both planar hy­dra­zinocarbonylalkyl substituents are essentially planar and assume the E orientation.     

Comparison of soluble manganese(IV) and acidic potassium permanganate chemiluminescence detection using flow injection and sequential injection analysis for the determination of ascorbic acid in Vitamin C tablets

The limits of detection (3s) for ascorbic acid were 5×10⁻⁸ M with acidic potassium permanganate using both flow injection analysis (FIA) and sequential injection analysis (SIA) whereas the soluble manganese(IV) afforded 1×10⁻⁸ M and 5×10⁻⁹ M for FIA and SIA, respectively. Determinations of ascorbic acid in Vitamin C tablets were achieved with minimal sample pretreatment using a standard additions calibration and gave good agreement with those of iodimetric titration.     

Current and efficiency improvement for a GaAsP/SiGe on Si tandem solar cell device achieved by light trapping techniques

A GaAsP/SiGe tandem solar cell on Si substrate has been further fabricated using light trapping techniques, such as texturing and adding a back surface reflector, and thinning the Si substrate. This is of importance to increase the J_sc of the Si_0.18Ge_0.82 bottom cell in this tandem system since bottom cell is current limiting. The J_sc of the bottom cell has been increased by relative 7.4%. This current improvement leads to a predicted efficiency of near 21% for this tandem device, with an absolute efficiency improvement of 0.3% over previous results without light trapping processes. The current of the bottom cell can be further improved by optimizing the bottom cell structure and texturing process, further thinning the Si substrate and increasing Ge concentration. (© 2016 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim)     

Performance improvement for epitaxially grown SiGe on Si solar cell by optimizing the back surface field

This letter reports on the performance improvement of an epitaxially grown SiGe on Si solar cell by optimizing the back surface field (BSF). First, a Si_0.18Ge_0.82 on silicon (Si) solar cell was fabricated with a 0.25 μm BSF layer. A 25 mV open‐circuit voltage (V_OC) improvement was observed on this BSF solar cell compared with the reference solar cell without BSF layer. Then, a Si_0.18Ge_0.82 on Si solar cell with double BSF layers was designed and fabricated. The measured efficiency of this solar cell is 3.4% when filtered by a GaAs_0.79P_0.21 top cell. To the best of the authors' knowledge, the 3.4% efficiency reported here is the highest efficiency for SiGe on Si solar cells when filtered by a GaAs_0.79P_0.21 top cell. The previous best reported efficiency for high Ge composition SiGe on Si solar cell was only 1.7% when filtered by a GaAs_0.79P_0.21 top cell.