Towards a better understanding of polymer-based light-emitting diodes: a theoretical insight into the basic phenomena

In this contribution, we try to illustrate that quantum-chemistry calculations can prove useful to comprehend better the phenomena occurring in the active layer of polymer-based light-emitting diodes. We review the results of recent theoretical calculations conducted at the correlated level on conjugated oligomers that address several topics of prime interest in the search of new routes towards the achievement of devices with enhanced characteristics. These studies performed on oligomers representative of poly (para-phenylenevinylene) and polythiophene deal with: (i) the modeling of the optical properties of the conjugated polymers involved in the emitting layer; (ii) the investigation of the relative locations of, and relaxation phenomena taking place in, the lowest singlet and triplet excited states; and (iii) the analysis of the effects of derivatization of the conjugated backbone. The theoretical approach we follow allows us to rationalize a wide range of experimental measurements and to provide guidelines in the design of novel attractive materials.