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DC ELECTROLUMINESCENCE IN ZnS : Mn

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HAL Id: jpa-00215572

https://hal.archives-ouvertes.fr/jpa-00215572

Submitted on 1 Jan 1974

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DC ELECTROLUMINESCENCE IN ZnS : Mn

A. Vecht

To cite this version:

A. Vecht. DC ELECTROLUMINESCENCE IN ZnS : Mn. Journal de Physique Colloques, 1974, 35

(C3), pp.C3-173-C3-173. �10.1051/jphyscol:1974324�. �jpa-00215572�

(2)

JOURNAL DE PHYSIQUE Colloque C3, supplément au n° 4, Tome 35, Avril 1974, page C3-173

DC ELECTROLUMINESCENCE IN ZnS : Mn

A. VECHT

Division of Materials Science, Thames Polytechnic, London, SE 18 England Résumé. — En 1969, N. Y. Werring et l'auteur ont fait la revue de Pélectroluminescence en courant continu (dcel) dans le sulfure de zinc [1 ]. Cette année, cette revue est remise à jour [2]. Les caractéristiques de dispositifs d'affichage dcel [3] sont indiquées brièvement et leurs propriétés sont comparées à celles des cellules en courant alternatif développées il y a quelque quinze années.

L'importante différence de préparation des matériaux et des lampes est signalée [4].

Abstract. — In 1969 N. J. Werring and I reviewed direct current electroluminescence (dcel) in zinc sulphide [1]. This year we brought this review up to date [2]. We hâve outlined the cha- racteristics of dcel displays [3] and compared their properties to the ac devices developed some fifteen years ago, indicating the important différence in the material préparation and panel cons- truction [4].

At présent two main types of devices are being manufactured on a prototype basis :

a) DC devices showing luminance of about 100 ft Lamberts at 100 V. Such devices still yield between 30-50 ft Lamberts after 3 000-5 000 hours and

b) Pulsed direct current devices showing typically a mean brightness of about 50 ft Lamberts at 120 V at 3 us at a duty cycle of 0.5 %. Thèse devices are being optimized for multi-character displays. So far 36 character displays hâve been produced (35 x 36 dots) and 1 200 character display is being planned. The efficiency of both dcel display types is about 0.1 %.

Although considérable effort has been made to obtain a useful range of colours, only the ZnS : Mn System emitting with a peak at 580 nm (yellow) has shown sufficient stability, brightness and main- tenance. Blue, green and red de panels of lower brightness hâve been produced, for example, from ZnS : Pb, ZnS : Er, ZnS : Tm and Ba

2

ZnS

3

: Mn.

No definite mechanism can, as yet, be assigned to the light emitting processes involved. It can now be shown that dcel can be obtained from Systems other than ZnS : Mn. Similar, although less efficient, pro- cesses occur in compounds such as ZnSe, ZnS and GaS as well as Ba

2

ZnS

3

where thèse are coated with a copper rich phase.

Références [1] VECHT, A. and WERRING, N. J., B. J. Phys. D. 3 (1970)

105.

[2] VECHT, A., J. Luminescence 7 (1973) 213.

[3] VECHT, A., WERRING, N. J., ELUS, R., SMITH, P. J. F.,

Prac. IEEE 61 (1973) 902.

[4] VECHT, A., J. Vac. Sci. and Technology 10 (1973) 789.

DISCUSSION J. P. NOBLANC. — Pour une brillance donnée, y a-t-il une influence de la taille des grains de poudre sur la tension de fonctionnement des cellules électro- luminescentes ?

A. VECHT. — This is a very difficult question to answer accurately. If we increase the particles size we hâve two effects over and above the actual effect of particle size :

a) Large particles will give rise to différent current paths and lead to a very « spotty » appearance.

b) The profile of the dopant gradients will vary e. g.

Cu at the surface and Mn gradient will be différent for différent particle sizes.

Thèse will mask actual size factors. We hâve however optimized our results in the région of

0.5-2.0 p. as in this région very uniform light émission is obtained.

F. GAUME. — Pourquoi obtient-on une émission orangée en dopant par le néodyme ? Peut-on supposer que le néodyme utilisé contienne des traces d'une autre terre rare ? Si oui, un transfert d'énergie Nd — autre TR — pourrait expliquer l'émission.

A. VECHT. — We hâve also asked your question ! We obtained peaks at 600.5 and 602.5 nm {Appl.

Phys. Lett. 10 (1971) 421). Although we cannot rule out cross contamination with other rare earths, the spectra and the fine structure obtained was repro- ducible over a range of sampies and we believe is due to Nd. Clearly the rare earth doped DC el spectra of ZnS await detailed analysis.

Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:1974324

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