Characteristic Differences in the Surface Space Charge Layer of the Red and Green Forms of Lutetium Diphthalocyanine

Abstract

The surface photovoltage of red and green forms of lutetium diphthalocyanine has been measured in a low pressure (2 · 10−9 Torr) environment and these two electrochemically interesting compounds have characteristic differences in their surface space charge layers. The green lutetium diphthalocyanine has an electron depletion layer, while the red material, prepared by iodization, has an electron accumulation layer. The photovoltage spectra are distinctive and are correlated with the differing optical absorptions of the colored films. The dependence of the dynamical response of the photovoltage on incident light indicates that photoinduced changes in the electronic populations of slow traps and/or surface states appear to be present.