# Photoluminescence of _Cis_-Polyacetylene Semiconductor Material
## 1 Introduction  
Over the past few years, conjugated oligomers and polymers have attracted considerable attention due to their applications in photovoltaic cells, light-emitting diodes (LEDs), field-effect transistors (FETs), electrochromic devices, chemical sensors, microelectronic actuators, etc. [1, 2]. A large amount of experimental and computational work has been devoted to studying the electronic properties of conjugated polymers using density functional theory (DFT) by means of approximate values of energy and state density. However, this type of research is quite complicated because the polymers do not have a well-defined structure, many of them are insoluble and polydisperse, and there are far fewer computational techniques for infinite polymers than well-defined molecules. In recent years, DFT has gradually replaced semiempirical methods, Hartree-Fock (HF) theory and perturbation theory in research on conjugated oligomers and polymers. Despite the many successes of DFT, HF theory gives a better approximation of the electronic properties of the CPs. To understand the behavior of the ground state of the electron andthe interface of the material via photo-induced charge transfer, it is important to study CPs using DFT and nonadiabatic coupling calculations. To explore the electronic structure of the CPs, ab initio DFT molecular dynamic simulation can be studied in combination with quantum dynamic calculations of the electronic relaxation to investigate the electron transfer of CPs. For example, [PERSON] et al. [3] studied the photo-induced charge transfer of an Au/Si metal-semiconductor nano-interface through a reduced density matrix (RDM), which was explained via Redfield theory and nonadiabatic coupling calculations based on the ab initio equations of a density function. The nonadiabatic couplings between electronic orbitals were processed on the fly along nuclear trajectories of the system [3]. In this study, we considered a model of a polyacetylene (PA) which has no commercial use yet, although PA is used as a processing solution for film-forming conductive polymers and molecular electrons. PA polymers are one of the commonly used polymers for photovoltaics, LEDs (light-emitting diodes), diodes, and transistors; in these applications, one needs to design and operate materials with modified electronic properties [3]. Therefore, electronic properties can be modified by using different types of approaches such as changing the composition of the polymer by adding doping, photoexcitation, or an injected charge, which occurs after applying different kinds of processes, such as photoexcitation, injection of charge, thermal motion (e.g., glass transition) or tight packing in the amorphous form of the material [4]. During the last few decades, many researchers have worked on the electronic conductivity of polyacetylene, and it has received much attention among them, particularly because of the possibility of increasing its electronic conductivity by doping and the low dimensionality of the electrical conductivity [5]. In 1977, for the first time, researchers published a study on the electrical conductivity of doped polyacetylene [6]. Recently, [PERSON] et al. [7] explained the electronic and physical properties of trans-polyacetylene. In that article, they explained the infrared photoluminescence of PA which was used to study the electronic structure of PA. They concluded that the photogenerated excitons that were generated at or near _cis_ defects could become trapped at the _cis_ (--CH=CH--) bond and undergo radiative recombination [7]. The observed photoluminescence emission energies were a function of the conjugation length of the _cis_ defect and the extent of local interchain \(\pi\) stacking. They proved that the _cis_ bond served to pinpoint and localize the photogenerated excitons formed on the polyacetylene chain [7].