Isoabsorption and spectrometric studies of optical absorption edge in Cu6AsS5I superionic crystal

► Cu6AsS5I single crystals were grown by chemical vapour transport. ► Two phase transitions in Cu6AsS5I at 153 and 260-280 K were observed from isoabsorption studies. ► Above 153 K the absorption edge has an exponential shape and a characteristic Urbach bundle is observed.