UV photoelectron spectroscopy of several one- and two-component organic photoconductors

Abstract

Solid state photoelectron spectra have been measured at several UV wavelengths for vapor‐deposited films of the organic photoconductors phenothiazine, anthracene, and carbazole and for the 1:1 donor:acceptor complexes of phenothiazine, carbazole, and acridine with the common acceptor pyromellitic dianhydride (PMDA). Differences in photoemission threshold energies of the one‐component photoconductors are used to estimate hole trap depth energies for systems where one of the compounds is doped with another one. Further, the photoemission threshold values are used for predicting the energy differences of charge transfer transitions in donor:acceptor crystals with a common acceptor. The reliability of this kind of estimation for the above mentioned substances is tested. In addition, by comparing the threshold values obtained for the D:A complexes with those of the neat donors, it is found (in confirmation of an earlier result) that complex formation with PMDA tends to increase the ionization threshold of the respective donor by 0.2–0.3 eV.