Design, synthesis and investigation on optoelectronic properties of thiophene based heterocycles

Abstract

The use of π–conjugated semiconducting materials in flexible and large–area optoelectronic devices is proliferated worldwide owing to the easy structural modifications and solution processability possible, leading to the change in opto– electronic properties. Most of the applications such as flexible displays and solid-state lighting sources based on organic light-emitting diodes (OLEDs) and nonlinear optical (NLO) devices are still in the developing stage due to the lack of ideal materials that exhibit the processability and an ability to interface with other materials. The research is continuing as ever to develop and characterize materials with large and fast optical responses which can satisfy different technological necessities. Furthermore, a definite correlation between the linear/nonlinear optical mechanism and the contribution of structure and nature of some thiophene based heterocycle is yet to be clearly interpreted. In this context, the present research work is focused on the design and synthesis of new class of thiophene based donor–acceptor (D–A) heterocycles for optoelectronic applications. A total of eighteen D–A type organic compounds were designed with various design strategies. They were successfully synthesized following appropriate synthetic protocols and characterized using different spectral analyses. The structureproperty relationships of the synthesized compounds were established by the optical absorption (UV–Vis), electrochemical (CV) and theoretical (DFT) studies. The third order NLO property i.e., the “effective two–photon absorption” of the compounds was confirmed by single–beam Z–scan analysis. The compounds VK3, VK8, VK10, VK12, VK13, VK14, VK15 and VK17 exhibit high nonlinear absorption coefficient (βeff) and a strong optical limiting behaviour. The preliminary studies on the electroluminescent properties of VK15 show that the molecule VK15 emits green light with low threshold voltage.