**4. Theoretical design of new multilayer architecture based on the synthesized materials**

Recently, Organic light-emitting diodes (OLEDs) have been considerably developed and considerable progress in the efficiency and durability is obtained [28, 29]. In order

to improve the injection and transport of the charge carriers from the anode or cathode, special multi-layer architectures are needed [30]. In this way, we are going in this part to the theoretical design of a new multilayer architecture using the investigated materials as an active layer. The first step of the calculations consists of the optimization of the geometries of the two single-walled carbon nanotube (SWCNTs) (5,5) and (6,4) having a diameter ϕ = 0.71 nm and length L = 100 nm (150 atoms), with the DFT-B3LYP-6- 31G(d) level of theory. The two optimized chemical structures are presented in **Figure 3**.

From the optimized chemical structure of the two forms of single-walled carbon nanotubes, the electronic parameters such as EHOMO, ELUMO, and the energy gap Eg = EHOMO-ELUMO were deduced and summarized in **Table 2**.
