To minimize changes in HOMO and LUMO levels, we selected isomeric or structurally analogous donoracceptor systems. The carbazole-substituted aromatic amines, DTAPC, AAPC, DAAPC, and the oligoarylamine DDATA, were selected as electron-donating dopants (Fig. ). DACT-II having a donor structure akin to DTAPC, was selected as a reference compound that will not form the intermolecular CT excited states with all investigated acceptor host molecules.