Absorption edge of silicon from solar cell spectral response measurements

Abstract

The optical absorption coefficient of crystalline silicon near the band edge is determined to values as low as 10−7 cm−1 by sensitive photocurrent measurements on high efficiency silicon solar cells. Structure due to three- and four-phonon assisted absorption processes is observed. Discrepancies between absorption coefficient values around 10−2 cm−1 reported in the literature are resolved. The role of disorder theory in understanding the absorption edge of crystalline semiconductors such as silicon is discussed.