Photothermal deflection spectra of solid

The optical absorption spectra of C-60 Single crystal and thin film in the weak-absorption region have been measured by photothermal deflection spectroscopy. The optical energy gaps, corresponding to optically forbidden transitions of weak absorption, were derived from Tauc plots. On comparison with the photothermal deflection spectrum of an amorphous semiconductor, the similarity suggests that the gap region of solid C-60 can be described in terms used for amorphous semiconductors such as an Urbach edge and sub-gap defect absorption. The weak-absorption characteristics of solid C-60 are discussed.