ABSTRACT
High performance of organic tandem solar cell is largely dependent on transparent and conductive intermediate layer (IML). The current work reports the design and fabrication of an IML using a simple solution process. The efficiency of a homo-tandem device with poly(3-hexylthiophene):phenyl-C61-butyric acid methyl ester as an active layer and poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate)/poly(ethylenimine) as an IML was initially found to be 3.40%. Further enhancement of the cell efficiency was achieved using silver nanoparticles (Ag-NPs) of different sizes and graphene quantum dot embedded IML. A maximum efficiency of 4.03% was achieved using 7 nm Ag-NPs that contribute to a better recombination process. Also, the performance of the tandem cell was solely based on the electrical improvements indicated by the current - voltage measurements, external quantum efficiency and impedance analysis. The use of Ag-NPs in the IML has been shown to lengthen the life time of electron-hole pairs in the device. This study thus paves way to develop such efficient IMLs for more efficient tandem solar cells.
ABSTRACT
Monolayer molybdenum disulfide (MoS2) is an emerging two-dimensional material beyond graphene, which could potentially be applicable to lightweight, flexible optoelectronic device. In this study, we have demonstrated a planar metal-semiconductor-metal (MSM) photodetectors based on large area monolayer MoS2. The monolayer MoS2 was grown via chemical vapor deposition method, showing excellent structural and optical properties. The current-voltage measurement was characterized at various monochromatic lights in visible spectrum. The device exhibited good responsivity ~7.7 mA/W for wavelength of ~470 nm, which is relatively comparative to mechanical exfoliated monolayer MoS2 based photodetectors. Additionally, the photoresponse measurement showed that the rise/fall time was about 1/0.7 s.
ABSTRACT
Levansucrase is responsible for levan formation during sucrose fermentation of Zymomonas mobilis, and this decreases the efficiency of ethanol production. As thiol modifying agents decrease levan formation, a role for cysteine residues in levansucrase activity has been examined using derivatives of Z. mobilis levansucrase that carry serine substitutions of cysteine at positions 121, 151 or 244. These substitutions abolished the levan forming activity of levansucrase whilst only halving its activity in sucrose hydrolysis. Thus, polymerase and hydrolase activities of Z. mobilis levansucrase are separate and have different requirements for the enzyme's cysteine residues.
