Design and Implementation of an Experimental Setup for Automated Photothermal Spectroscopy

Abstract

Recent developments in solar energy research have led to new technologies in solar cells. Materials based on chalcopyrite ternary semiconductors have gained great interest because of their excellent optical properties. It has been shown that the compound’s defect structure affects strongly the optoelectronic properties of these alloys. In order to obtain more efficient devices these defects need to be detected and identified. The best way to characterize those novel materials is to use new techniques based on the exploitation of the photothermal effect. The main objective of this work is to study and implement an automated photothermal spectrometer. The first measurement technique that can be done with this apparatus is the photoacoustic spectroscopy. Wavelength scanning and data acquisition and logging are done automatically by a program written in LabVIEW. The second measurement technique is a transition from the former one. It is done by modifying only a few devices. Thus, one can make the photothermal beam deflection spectroscopy simply by adding a laser source and the position sensor detector that goes with it. The last measurement technique that can be done with the implemented setup is photothermal imaging analysis. We just add a motorized X-Y stage and a suitable focusing optics. The assembled apparatus conceived in this work constitutes an essential tool for analyzing and characterizing ternary and quaternary absorbing materials for photovoltaic and microelectronic applications. This setup can also be used by a large number of scientists in various disciplines such as biology, medicine, physics and optics, since the analysis is nondestructive and without contact. It provides researchers with information on non-radiative de-excitation processes regardless of the form of the samples (solid, liquid, gel or gas). Finally, the test and calibration procedures necessary to have a functional and accurate system are reviewed.

Keywords

• Photothermal,Spectroscopy,Photoacoustic,Chalcopyrite,Characterization

References

1. Rosencwaig, A. (1980). Photoacoustics and Photoacoustic spectroscopy, New York, Wiley. Sell, J.A. (1989). Photothermal Investigations of Solids and Fluids, Academic Press. Zegadi, A. (1994). Photoacoustic Study of CuInSe2 Single Crystals, PhD thesis, University of Salford, UK. Zegadi, A. Slifkin, M.A. Tomlinson, R.D. (1994). Review of Scientific Instruments, 65, 2238-2243. Boccara, A.C. Fournier, A.D. Badoz, J. (1980). Applied Physics Letters, 36, 130-131.