Effectiveness of Iodine Termination for Ultrahigh Efficiency Solar Cells as a Means of Chemical Surface Passivation

Abstract

The use of iodine as a passivating agent for chemical modification of silicon surface is demonstrated. The measurement of carrier lifetime using microwave photoconductivity decay method shows an effective passivation with iodine treatment which is 5 times greater than hydrogen passivation. Unlike hydrogen termination, the negative charge created by the iodine termination enhances the solar cell performance. For n-type silicon, the charge effect results in electric passivation. For p-type silicon, the charge effect forms a barrier which acts as back surface field. For cells with the same area, open circuit voltage (VOC), short circuit current density (JSC), fill factor (FF), and efficiency (η) of iodine terminated one were 610 mV, 39.5 mA/cm2, 76.1%, and 18.3% while those of hydrogen passivated one were 600 mV, 33.4 mA/cm2, 73.1%, and 14.7%, respectively.