Push-pull unit decorated oligomer for organic electronics

Push-pull unit decorated oligomers are an attractive class of materials which have been widely explored for their applications in optoelectronic devices such as organic photovoltaic cells (OPVCs), organic lightemitting diodes (OLEDs), organic field effect transistors (OFETs) as well as a hole-transporting material (HTM). Electronic interaction between the electron push and electron pull units in conjugated oligomer dramatically lowers the band gap or HOMO/LUMO energy and thus the molecule absorbs the deep-red or NIR spectral range. A large number of electron push derivatives such as triarylamine, thiophene, alkylated-thiophene, polythiophene, naphtho-dithiophene, poly(phenylenevinylenes), benzo-dithio-phene, dithienylbenzothiadiazole, 9,9-dioctylfluorene, N-alkylcarbazole etc. are available in literature. Similarly, researchers have developed many electron pull derivatives such as benzotriazole, 5-alkylthieno [3,4-c]pyrrole-4,6-dione (TPD), diketopyrrolopyrrole (DPP), 6-alkylpyrrolo[3,4-d]pyridazine-5,7-dione (PPD), 2-alkylisoindole-1,3-dione, benzo[1,2,5]thiadiazole, iso-indigo, 5,6-difluorobenzo[1,2,5] thiadiazole, [1,2,5]thiadiazolo-[3,4-c]pyridine, tetrazine, 6-alkylpyrrolo [3,4-d]pyridazine-5,7-dione, bisbenzothiadiazole etc. to construct pushpull unit decorated oligomers or optoelectronic material for practical application. Both the electron push and electron pull units are essential to tune the energy levels of the HOMO/LUMO of the particular materials. One of the major obstacle of the push-pull unit decorated oligomer is its solubility which limits the practical use to some extent. However, the alkyl group introduction on to the push and pull units leads to better solubility. Moreover, the solubility is strongly depends on the position of alkyl groups as well as on their length. This chapter will focus on the synthesis of various electron push and electron pull units towards the construction of push-pull unit decorated oligomers and their application as organic optoelectronic materials.