The Temperature Dependence of Hole Injection into Anthracene Crystals

The temperature dependence of dark- and photo-currents was studied for the hole injection into anthracene crystals between 0 and 30°C. It was observed that the photocurrent or, as has been previously established, the electron-transfer rate from an excited anthracene crystal to an acceptor had a small temperature dependence, while the dark current or the electron-transfer rate from the crystal in its ground state to an acceptor had a definite value of activation energy. The observed small activation entropy for the dark reaction was interpreted in terms of Marcus’ theory, and the small polarizability of the organic crystal was, accordingly, suggested to increase the probability of the electron transfer.