Abstract
The construction of multilayered organic polymer devices often involves long experimental searches for the combinations of polymers that give the optimum device performance. Combinations of different fluorene-based conjugated polymers such as alternating triphenylaminefluorene (TPAF)- and oxadiazolefluorene (OxF)-based conjugated copolymers were considered as components of multilayered organic light-emitting diodes (OLEDs). It was found that the OxF3-TPAF2 combination gave the best OLED performance. Theoretical/experimental investigations of the properties of single (isolated) polymer chains did not yield conclusive evidence for choosing OxF3-TPAF2 over other similar combinations. For multilayered OLEDs, the interfacial region is critical to the performance of a device. Hence, in this work, we focus on studying the properties of the various pairs of monomers of OxFn and TPAFn (n = 1-3) copolymers. We analyze their electronic structures and binding energies using the dispersion-corrected density functional theory (DFT/B97D) method. Our results illustrate that the (empirically favorable) combination of OxF3 and TPAF2 monomers, with their chain lengths and HOMO-LUMO energy gaps well matched, has the closest intermolecular distance and the highest binding energy of all the combinations of OxFn and TPAFn (n = 1-3) monomers. This study illustrates that (heterogeneous) dimer properties can be used to determine the best matching between polymers and hence optimal performance in multilayered devices.