**1. Introduction**

The progress of the research in the field of Organic electronic devices based on organic materials has been actually a considerable challenge for scientific chemistry and physics [1–3]. The use of conjugated polymers such as Poly(p-phenylene vinylene) (PPV) derivatives was permitted to obtain flexible and transparent green OLEDs [4, 5]. Else, the extension of the effective conjugated length in poly(3-alkyl thiophene) (PAT) family, enhances the π-π stacking effects in the condensed state [6, 7], consequently, a poor red emission in the condensed state, is obtained with a weak photoluminescence quantum efficiency (PLQY), which is at around 1–2%, limiting also the use of PAT conjugated polymers for OLED applications [6, 7]. In order to enhance the photophysical properties of the investigated organic active layer of the organic light-emitting diode (OLEDs) and to improve the performance of the OLEDs displays, many efforts have recently been undertaken on the photoactive layer [8, 9]. Furthermore, experimental and theoretical efforts on the multilayer structure were employed in order to enhance the performance of the focused displays [8–10]. Recently, focused researchers show that Carbazole or bicarbazole based conjugated polymers are among superior host materials, showing promising performances in newly organic light-emitting devices [11–14]. Moreover, the use of small molecules is one of the new solutions to minimize the geometric distortion and the possible defect on the main chain and to enhance the investigated photophysical properties [8–10]. In this area of research, we have firstly, incorporated Poly(9-vinyl carbazole) (PVK) under the chemical polymerization of 3-methyl thiophene monomers, using the anhydrous Ferric chloride (FeCl3) in chloroform solution [15]. The new polythiophene derivative is named PVK-MeT [15]. Photophysical investigations based essentially on spectroscopic analysis show a great enhancement in the luminescence properties, which encourage the investigation of the new material for a new generation of OLED devices [15, 16]. On the other hand, we present the chemical synthesis of a new blue-emitted organic small molecule [17]. Two newly synthesized organic materials are obtained and named respectively 1,4-Bis(a-cyano-4-methoxystyryl) benzene (DOMCN) and 1,4-Bis(a-cyano-4-bromostyryl)benzene (DBrCN) [17]. The chemical synthesis of the DOMCN and DBrCN molecules is done for possible investigation as an active layer for a new generation of a new performant organic blue light-emitting diode. The chemical synthesis and the photophysical properties were briefly described herein, and theoretical computations are undertaken to determine the electronic parameters of the synthesized chemical structure. Moreover, the synthesized organic materials presented in this chapter were theoretically used as an active layer in a newly designed multilayer structure for organic light-emitting display using essentially Density functional theory (DFT) computations on the geometric and electronic structure of the optimized chemical structure. Theoretical investigations show that The insertion of single-walled carbon nanotubes (SWNTs) on the prepared multilayer structure enhances the injection of the charge carriers (electron) and improves the physical and electronic performance of the electronic devices based on the investigated organic materials.
