ELECTRON AND HOLE GENERATION IN ANTHRACENE CRYSTALS

Abstract

Experimental results regarding electron and hole production in anthracene crystals are reviewed with emphasis on the relevance of these studies to the fundamental question of the nature of the excess electron states in these low mobility crystals. It is pointed out that a number of experiments suggest that above a threshold of about 4 eV in anthracene crystals, electronic transitions involve transitions of an electron from a ground state to a quite broad band rather than to bound states, some of which subsequently autoionize to create carriers, as has been thought to be true in the past. Most of the electrons created in this process apparently immediately recombine with the hole which was simultaneously created because they both have very small mean free paths for energy losing collisions and thus remain trapped in each other's coulomb field. Another experimental test of this hypothesis is proposed. The various types of carrier generation processes which have been observed and which will ultimately be useful in studies of highly excited states in anthracene crystals are reviewed.