Growth and characterization of CdZnS thin film buffer layers by chemical bath deposition
In this paper we report the study of CdZnS thin films grown on the soda-lime glass (SLG) substrates by chemical bath deposition (CBD) process for buffer layer applications in CuGaSe/sub 2/ (CGS) solar cells. Structural, surface morphology, optical, and electrical properties of as-deposited CdZnS films were investigated by XRD, SEM, spectrophotometer, and four probes resistivity measurements as a function of Zn-composition in the solution. The CdZnS films have hexagonal structures. The grain size of CdZnS films was found to increase with increasing Zn-content in the solution. The films with 30% of Zn in the solution showed a better than 80% transmittance for wavelengths longer than 600 nm and film thickness less than 50 nm. The values of energy band gaps obtained are 2.40, 2.55, and 2.70 eV for Zn-content of 0, 30, and 50%, respectively. The resistivity of CdZnS films was found to increase as the Zn content increases.
Experimental Study on Structural, Optical and Electrical Properties of Chemical Bath Deposited CdZnS Thin Films
CdZnS thin films have been prepared from an aqueous solution containing cadmium chloride, zinc acetate and thiourea by chemical bath deposition (CBD) method on a glass substrate at 82°C. Amount of cadmium chloride and zinc acetate were systematically varied as y=0.2, 0.4, 0.6, 0.8 (y=a/(a+b), a=volume of zinc acetate, b=volume of cadmium chloride) and subsequent effects on the film's property were studied by diffractometer, scanning electron microscope, spectrophotometer, four point probe and hall effect measurement. X-ray diffraction result shows that an increase in the Zn-content decreases the crystalline quality of the films. Transmittance and absorbance data was obtained by using UV-Vis spectrometer. Transmittance of 85-90% is found beyond the 700 nm wavelength. Optical bandgaps calculated from these data show a gradual increase in value with a gradual increase in Zn content. The electrical resistance of the so prepared films were measured by four point probe method. The result indicates that the resistance increases with increasing Zn content.
An Essay on the Nature and Significance of the Normative Nature of Economics
It is conventional in economics to distinguish between the normative and the positive. The normative has to do with goodness and badness, and with what ought and ought not to be done;1 and the positive has to do with objective description and/or explanation, with what is and with what is necessary given some normative end. The normative has to do with desirability; the positive has to do with truth (in the sense of either descriptive accuracy or serviceability of a means to a given end).2