Effectiveness of iodine termination for ultrahigh efficiency solar cells as a means of chemical surface passivation

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 (V _OC), short circuit current density (J _SC), fill factor (FF), and efficiency (η) of iodine terminated one were 610 mV, 39.5 mA/cm ², 76.1%, and 18.3% while those of hydrogen passivated one were 600 mV, 33.4 mA/cm ², 73.1%, and 14.7%, respectively.