Design and fabrication of mos solar cells

ABSTRACT DESIGN AND FABRICATION OF MOS SOLAR CELLS TÜTÜNCÜLER, Hayriye M. S in Physics Engineering Supervisor: Assoc. Prof.Dr. M. Sadettin ÖZYAZICI February 1994, 81 pages In this thesis, effects of insulating (oxide) layer on Schottky barrier (metal -semiconductor contact) has been investigated. To make this investigation more specific minority carrier metal -oxide-semiconductor (MOS) solar cells were designed and fabricated in the form of Al-oxide-p-type silicon crystal. Resistivity of samples were measured before fabricating MOS solar cells. Aluminum coating was made by Vacuum Coater System with Diffusion Pumping System. To maximize the efficiency of the MOS solar cell, the open circuit photovoltage, short circuit photocurrent and the fill factor must be as high as possible when the total incident light energy is kept constant. But these factors depend on the same parameters and related to each other. When one parameter is increasing as a function of certain parameter, the others may be decreasing. Therefore, straightforward maximization of efficiency is not possible. To see the effects of insulating layer thickness on the short circuit current, different oxidation techniques were used. After device fabrication was completed I-V and C-V iiicharacteristics of solar cells have been measured. Open circuit voltage(VQC) and short circuit current (Iscj which affect the conversion efficiency have been determined. Experimental results showed that presence of positive charges in oxide layer enhance the Voc as indicated by the increase in barrier height. High barrier height decreases the dark current altering the I-V characteristics in the dark. Efficiencies of MOS solar cells were calculated as 7.3 %. This value is low as compared to published results. The reasons of getting low conversion efficiencies have been also discussed. Key words: MIS/MOS solar cells, photocurrent, photovoltage, efficiency. IV