Papers by Keyword: Spectral Response

Abstract: This paper describes the fabrication, characterization, and simulation of 4H-SiC pin-photodiodes for solar UV radiation detection. The devices were produced with an aluminum implanted emitter unlike most previously published detectors which use epitaxy for all applied doping regions (see e.g. [1-3]). They were electrically characterized at different temperatures with and without UV-illumination and afterwards a spectral analysis of the photocurrent was performed. A quantum efficiency up to 55% at 260 nm will be shown. Furthermore, the capability of the diodes for visible blind sun UV monitoring e.g. within a building, is demonstrated.

Abstract: In this work, fabrication and characterisation of graphene photodiodes and transfer length method structures is presented. Graphene growth is carried out using a thermal chemical vapor deposition process on copper foils and subsequently transferred onto silicon-dioxide/silicon substrate. Comparison of electrical and optical characteristics of the photodiodes, which are fabricated on both n-type and p-type silicon, is shown. The photodiodes fabricated on n-type silicon show good rectifying behaviour when compared with photodiodes fabricated on p-type silicon. Spectral response of graphene photodiodes is measured to be less than 0.2 mAW^-1 which is attributed to the light absorbance of 2.3% for single layer graphene. Transfer length method device structures are also fabricated and contact resistance is calculated and plotted as a function of spacing between the contacts. The calculated contact resistance (R_cW) is 0.87 kΩ.µm. The latter structures are also characterised under various ambient conditions, before and after annealing. The value of contact resistance reduces from 0.87 kΩ.µm to 0.75 kΩ.µm after annealing. This reduction is attributed to the improvement in bonding between graphene and metal. Measurements under vacuum show an increase in contact resistance which is attributed to the removal of adsorbed water molecules on the surface on graphene. The sheet resistivity of graphene is calculated to be between 1.17 kΩ/□ and 3.67 kΩ/□.

Abstract: The goal of I-V characteristic measurement of photovoltaic (PV) module is to reduce uncertainty not only for PV laboratories but also for manufacturers. This paper presents the results comparison and data analysis between two PV laboratories. Even though both laboratories have obtained the ISO 17025 certificate, the I-V results show inevitable deviation. The cause of deviation depends on photovoltaic scale traceability of laboratory, system bias, internal quality control measures and other uncertainty sources. The analysis also shows that the PV scale traceability is the most important factor to reduce result deviation among laboratories and measurement uncertainty. The various contributions to the result deviation are critically illustrated for different traceability chains. Besides, the calibration method of reference photovoltaic devices (reference cell or module), spatial uniformity of irradiance and I-V data acquisition unit should be paid more attention as well.

Abstract: Transmittance is the key factor to the quality of solar glass. At present visible light transmittance (380-780 nm) and solar direct transmittance (300-2500 nm) were used to evaluate the light transmission property without considering the specificity of solar glass. In this work a new parameter of effective transmittance in the 380-1200 nm region which was consistent with the spectral response range of solar cells was proposed and calculated to evaluate the property. The value of effective transmittance lies between that of visible light transmittance and solar direct transmittance. Using effective transmittance instead could reflect the performance of solar glass on real applications properly.

Abstract: The existing mine derrick design only includes the guiding principles and the empirical formula, but has no the mechanism of structural dynamics characteristics under an earthquake conditions. Then the modal analysis and spectral response analysis of the derrick have been finished for gaining the derrick natural frequency, mode shapes, and time response curve based on ANSYS in the thesis. The analysis results provides important basis for the anti-seismic design, optimization design and avoiding resonance.

Abstract: The optical characterization of Molybdenum diselenide (MoSe₂) and polyaniline (PANI) has been carried in the wavelength range 200 nm to 2500 nm. The detailed analysis of the optical properties has been carried out only for a range 200 nm to 800 nm from which the indirect band gap around 1.42 eV for MoSe₂ and 1 eV and 2.5 eV for PANI was evaluated. It was interesting to note that π π* transitions lead to two distinct orders of energy gaps. The hybrid cells were fabricated using a photosensitive interface between MoSe₂ and PANI. Various parameters of these heterostructure hybrid cells have been evaluated and it was found that the photoconversion efficiency was around 1%. Using the solar cell characteristics, the presence of trapping centers at the n-MoSe₂/ p-PANI interface has been confirmed.