Photoelectric Characteristics of Composite Carbazole Polymerfilms Containing 1,8-Naphthoylene-1′,2′-Benzimidazole

Abstract

The electric conduction and photoconduction of sandwich-type poly-N-epoxypropylcarbazole (PEPC) and 3, films containing 33 wt.% of the dye 1,8-naphthoylene-1 ′ ,2 ′ -benzimidazole (NBI) have been investigated. It has been established that the PEPC films, as compared to the 3,6-di-Br-PEPC films, have a higher electric conduction and a lower photosensitivity and an electric field exerts a stronger quenching effect on the photoluminescence of the first-mentioned films. Analysis of the voltampere and lux-ampere characteristics and the kinetics of electric conduction of these films has shown that the space charge and recombination via dye molecules in them influence their electric conduction and photoconduction. The volume recombination of charges is radiative in character.Introduction. In designing active optical information media based on polymer composites possessing photosemiconductor properties, it is necessary to select their components such that charge-carriers (holes and electrons) could be transported under the action of an external electric field. In these systems, charge carriers can be formed by injection of charges into films from contacts or by exposure of them to a radiation acting on the photogeneration centers, as which organic dyes can serve [1,2]. It is important to correctly select dyes serving as the recombination centers in optical-data representation systems based on electroluminescent materials [3,4]. A number of requirements are imposed on the dyes used in the above-mentioned media and materials. These dyes should possess a number of valuable physicochemical and spectral properties that would allow them to provide an effective transport of charge carriers and have a large extinction ratio and a high quantum yield of photoluminescence in the visible or near-IR regions of the spectrum.The aim of the present work is to investigate the spectral and photophysical characteristics of new, onelayer, composite polymer films based on photosemiconductors and organic dyes satisfying the above-indicated requirements and, accordingly, providing high electrical conduction and photoconduction and possessing electro-and photoluminescence.Investigation Objects and Experimental Procedure. We investigated the spectral characteristics as well as the electrical conduction and photoconduction of poly-N-epoxypropylcarbazole (PEPC) and 3,6-di-Br-poly-Nepoxypropylcarbazole (3,6-di-Br-PEPC) films containing 33 wt.% of the dye 1,8-naphthoylene-1 ′ ,2 ′ -benzimidazole (NBI)

Electrical conductivity and photoconductivity of films of composites based on poly[2-methoxy-5-(2′-ethylhexyloxy)-1,4-phenylenevinylene] with additions of zinc octabutyl phthalocyanine and C60

“…The photoconducting characteristics of the composite films are explained by the photogeneration and transport of holes in the polymer. Composite films with additions of organic dyes or metal complexes were created in order to shift the photosensitivity spectrum of the photoelectric converters or the electroluminescence radiation toward the near IR region [5][6][7][8][9]. …”

“…Their electron spectra agreed with published data. (3,7,8), and MEH-PPV + 3 wt.% C 60 + 3 wt.% Pc Bu Zn (4). Excitation of luminescence at l 1 (5-7) and l 2 (8).…”

“…The samples for the investigations were prepared in the form of structures with a free surface (glass substrate)-(composite film) and sandwich structures (glass substrate)-(conducting layer of SnO 2 : In 2 O 3 )-(composite film)-Ag [7]. The concentrations of C 60 and Pc Bu Zn amounted to 3 wt.%, which usually secures effective photogeneration and transport of electrons [6].…”

“…The concentrations of C 60 and Pc Bu Zn amounted to 3 wt.%, which usually secures effective photogeneration and transport of electrons [6]. The procedure for measurement of the optical density (D) and the photoluminescence intensity (I L ) in the range of light wave lengths l = 400-900 nm, the current density (j d ) before irradiation, and the current density (j) during and after irradiation with light on the side of the SnO 2 : In 2 O 3 conducting layer was described in [7]. As light sources we used semiconducting lasers with l 1 = 545 nm and l 2 = 645 nm, for which the respective current densities j 1 and j 2 were measured as the difference between j and j d .…”

“…The intensity (E = U/L) of the external electric field was varied in the range of 1×10 6 -2×10 8 V/m, where L is the thickness of the film of the composite (1.5-2.5 mm) and U is the electric voltage at the contacts. As in [7], the value of I L was measured before (I L0 ) and after (I LE ) connection of the external electric field with E = 1×10 8 V/m. From these measurements we calculated the value dI LE = (I LE -I L0 )/I L0 of the relative change in the intensity of photoluminescence in the electric field, which can characterize the photoconducting characteristics of the CF and the fraction of recombination luminescence in the radiation [10].…”