Molecular Simulation of Excimer Fluorescence in Polystyrene and Poly(vinylcarbazole)

Abstract

In fluorescence emission spectra of poly(vinylcarbazole) (PVK), two types of excimers are observed, the fully and the partially overlapped excimers, namely, excimers and exciplexes. In this work, we investigated the structural changes induced by the transition between electronic levels S(0) and S(1). Furthermore, the widely used assumption of similar potential energy surfaces in the S(0) and S(1) states and its use in molecular dynamics simulations are thoroughly examined for PVK and polystyrene (PS). The ground-state and excited-state intermolecular potentials between phenyl or carbazyl substituents in PS or PVK, respectively, are computed from high-level ab initio calculations and fit to analytic potentials. Finally, molecular dynamics simulations are performed at room temperature for PS and for isotactic and syndiotactic PVK. This treatment enabled the decoupling of excimer and exciplex contributions from the simulated spectra.

Effect of distance between acceptor and donor on optical properties of composite semiconducting polymer films

“…decay of the pure PVK film is multi-exponential, indicating that there are multi-excitations. A full overlap configuration and a partial overlap configuration of two adjacent carbazole groups are responsible for the excitations with different life times in PVK [22][23][24]. The average decay time of the PVK/Alq 3 (8%) film without PMMA is markedly decreased because the excitations in PVK are quenched by Alq 3 .…”

Preparation and photoluminescence properties of electrospun nanofibers of C60/PVK

“…Compared to the PL emission spectra of the PVK thin films, the PL emission peaks of the PVK nanofibers (Fig. 3D) 437 nm PL emission band in the PVK nanofibers is connected with intrachain excimers in which the two interacting carbazole groups form a full overlapping, sandwich-like configuration [12,14]. In the electrospinning produce, the charged jet of the fluid is ejected from the tip of the Taylor cone [19].…”

“…Poly(N-vinylcarbazole) (PVK) that is one of a number of vinyl polymers with aromatic pendant groups have elicited considerable interest as potential commercial photoconductor systems and exhibit interesting electrical properties, etc [11]. The electronic, structural, and spectroscopic properties of PVK have been investigated extensively [12][13][14][15]. The spectral range associated with the charge photogeneration process can be controlled by addition of acceptor molecules such as buckminsterfullerene (C60), which exhibits a variety of outstanding electronic, conducting, magnetic properties due to its unusual structure and extended p-electron system and its a high electron affinity (2.6-2.8 eV), indicating that C60 may function as good electron acceptor [11,16].…”

The broadened and red-shifted photoluminescence spectral emission of poly(N-vinylcarbazole) nanoparticles

“…Compared to the PVK solution and film, the PL spectrum of the PVK nanoparticles becomes wide and its PL peak red shifts to 430 nm. The 430 nm PL band has been considered to be connected with intrachain excimers, in which the two neighboring carbazole groups in one polymer chain form a full overlapping, sandwich configuration [15][16][17]. During the preparation of the polymer nanoparticles, a small quantity of the PVK THF solution is injected into a great quantity of water.…”

“…The excited states in PVK have been considered as excimers owing to the closed carbazole groups. Two configurations are responsible for the excimers in PVK namely, an excimer with a low-energy emission band (430 nm) that comprises an overlapping, sandwich-like configuration of two carbazole groups and an excimer in which the partial overlap of two carbazole groups is responsible for the observed, high-energy emission band (380 nm) [15][16][17]. The 380-nm emission band has been found to be dominant in the photoluminescence (PL) spectra of syndiotactic PVK, whereas, the intensity of the 430-nm emission band increases with increasing mole fraction of the isotactic diads in PVK [16].…”