Photoconductivity of Anthracene. III

Compton, D. M. J.; Schneider, W. G.; Waddington, T. C.

doi:10.1063/1.1743658

Cited by 59 publications

(6 citation statements)

References 11 publications

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“…It was approximately 40 years ago that the first detailed studies of the electrical and photoelectrical behaviors of organic and inorganic molecular solids began. [1][2][3][4][5][6][7][8] In large part these were aimed at getting a better understanding of important photochemical processes such as photosynthesis and vision and also to promote their use as photographic sensitizers. It is also not many years ago that interest in the electrical properties of polymers was effectively limited to their electrical insulating ability.…”

Section: Introductionmentioning

confidence: 99%

Photocurrent generation and charge transport in tin dioxide/ion-exchange polymer-zinc meso-tetraphenylporphyrin/gold cells

Lawrence¹,

Huang²,

Langford³

et al. 1993

J. Phys. Chem.

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A variety of experiments have been performed to investigate electrical conductivity in a system composed of zinc meso-tetraphenylporphyrin (ZnTPP) incorporated in an ion-exchange polymer. This polymer is a blend of poly(4-vinylpyridine-co-styrene) and a random ternary copolymer with cationic sites. Thin films of this mixture were cast from solution onto SnO2 optically transparent electrodes, and conductivity measurements were then made possible by the evaporation of gold contacts on top of the films. The variation of dark current as a function of applied voltage, observed using polymer films with or without ZnTPP, follows the behavior expected of an insulator containing traps. Analysis of the space-charge limited currents in these samples enables the determination of a total trap density of Nt = 3 X lOI4 ~m -~ and a trap depth Et of -0.73 eV. The addition of dye molecules to the polymer blend is found to have little effect on the density of deep traps as well as on the charge mobility which varies from 3 X cm2 V-' s-'. The temperature dependence of the dark conductivity, however, shows that the activation energy of the conduction process changes from a AE of -4 eV for the polymer alone, to a L!? of -2 eV for the polymer4ye system, in the same temperature range.Photoconductivity measurements performed in the visible on the polymer4ye system clearly indicate that light absorption by ZnTPP is responsible for the observed photocurrents. The response times of the photoinduced currents, during a light-on/light-off sequence, are characteristic of systems in which conductivity is strongly influenced by the trapping and recombination of charge carriers. The isothermal time dependence of photocurrent decay indicates the existence of an isolated narrow distribution of traps with an Et of -0.78 eV. Arguments are brought forth which indicate that these trapping centers may correspond to pyridinium sites present in the ion-exchange polymer. From these observations, a discussion concerning the energetic relation between the individual components involved and the effect of traps on the photogenerated charge carriers is presented to account for the photoconductor's overall behavior.to 4 X

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Section: Introductionmentioning

confidence: 99%

Photocurrent generation and charge transport in tin dioxide/ion-exchange polymer-zinc meso-tetraphenylporphyrin/gold cells

Lawrence¹,

Huang²,

Langford³

et al. 1993

J. Phys. Chem.

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“…The efect of temperature on the level of the surface photocurrent i n the presence of a n ambient gas.-The effect of temperature (in the range -130' to 55' C.) on the value of the photocurrent in the surface and sandwich cell in a hard vacuum has been reported in a previous communication (10). I t talies the form of an expo~lential relation i = i o exp ( -E / R T ) .…”

Section: Resultsmentioning

confidence: 99%

The Effect of the Ambient Gases on the Surface Photocurrent in Anthracene

Waddington¹,

Schneider²

1958

Can. J. Chem.

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Following the observation that the photocurrent in anthracene is marbedly alfected by an atmosphere of osygen over the system, the behavior of anthracene in the presence of atmospheres of other gases has been investigated. The effect has been shown to be confined to the surface photocurrent, and the active gases have been shown to fall into two classes: (1) gases which are electron acceptors, e.g. BFa, HCI, 0 2 , and NO, which all increase the photocurrent marlcedly; (2) gases and vapors which arc electron donors, e.g. NH3, (CH3)20, and (CHO)JN, which all decrease the photocurrent markedly. The effect of the pressure of the arnb~ent gas and of the ternperat~rre of the system on the photocurrent has also been investigated.

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“…However, the infra-red source also emitted visible light, which is known to produce charge carriers in anthracene. 4 In a later experiment, a monochromator was used to select desired wavelengths from the spectrum of a 50 W tungsten lamp. Glow peaks were found following lowtemperature irradiation only at wavelengths less than 40oO A, i.e., at wavelengths within the strongly absorbing, low energy singlet-singlet band of the crystal.…”

Section: R E S U L T S a N D Discussionmentioning

confidence: 99%