The effect of Mn concentration on ZnS: Mn electroluminescence decay

Abstract

Luminescence decay of ZnS: Mn films after electric field switching-off was investigated in dependence on the Mn concentration, which changes from 0.1 to 7 wt%. The decay of electroluminescence does not depend on the charge polarization and RC-time constant of the film cell but it is determined by the kinetics of radiative transition in the Mn2+ ion. It is established that an increase of the Mn concentration above 0.3 wtyo leads to the following effects: 1) the rate of decay increases, 2) the decay curves are described a t the given concentration by a sum of two exponents rather than a simple exponential law, 3) the decay time constants of both the exponential sections decreases. On the basis of the results obtained and of literature data analysis it is concluded that the observed effects in electroluminescence decay are due not only to the concentration quenching of luminescence but to the formation of new manganese centers or the occurrence of new transitions in them, characterized by a smaller excited-state lifetime than the lifetime of Mn2+ isolated ion.Es wird das Abklingen der Lumineszenz von ZnS:Mn-Schichten nach Abschalten des elektrischen Feldes in Abhiingigkeit von der Mn-Konzentration, die zwischen 0,l und 7 Gew.yo variiert, untersucht. Der Abfall der Elektrolumineszenz hangt nicht von der Ladungspolarisation und RC-Zeitkonstante der Schichtzelle ab, sondern wird durch die Kinetik des Strahlungsiibergangs im Mn2+-Ion bestimmt. Es wird gefunden, daD eine Erhohung der Mn-Konzentration uber 0,3 Gew.% zu folgenden Effek ten fuhrt : 1) die Abklinggeschwindigkeit nimmt zu, 2) die Abklingkurven lassen sich bei der gegebenen Konzentration eher durch eine Summe von zwei Exponenten als durch ein einfaches Exponentialgesetz beschreiben, 3) die Zeitkonstante des Abklingens beider exponentieller Abschnitte nimmt ab. Auf der Grundlage dieser Ergebnisse und einer Analyse von Werten aus der Literatur wird geschlossen, daD die beobachteten Effekte des Abklingens der Elektrolumineszenz nicht durch eine Konzentrationstilgung der Lumincszenz, sondern durch das Auftreten neuer Manganzentren oder durch das Auftreten von neuen ubergiingen in ihnen hervorgerufen werden, die durch eine kiirzere Lebensdauer der angeregten Zustiinde als die Lebensdauer der isolierten Mn2+-Ionen charakterisiert aind.

Energy Transfer Processes in (Zn, Mn)S Mixed Crystals

“…This can also be concluded from the nearly unshifted positions of the Mn2+ (3d5) absorption bands in P-MnS (eincblende modification) measured in [15] with respect to those in ZnS : Mn. In contrast to our explanation for the observed decrease of z,,ffwith increasing cMn, in [14,18] this effect was ascribed to the occurrence of Mn2+ pairs and higher Mn2+ clusters which are assumed to have a much higher probability for the 4T, --* 6A1 optical transition than isolated Mn2+. It should be pointed out that this assumption would not lead to an explanation of the red emission and, furthermore, of the observed strong decrease of the quantum efficiency qy with increasing cyn.…”

Method of Determination of Mn Concentration in ZnS Based on Kinetic Measurements of Luminescence

“…It is well-known that, generally, manganese in ZnS creates two kind of centres: Mn2 + ions and Mn2 +-Mn2 + pairs [2,3,7,15]. So, we can use the above described method to determine concentration of manganese in our e l e c t…”

“…I n o r d e r to determine the Mn concentration in the cells investigated, we used τ1 the lifetime dependence on Mn2 + concentration introduced by Vlasenko et al [2]. Figure 2 shows a comparison of the method described in Sec.…”

“…In many papers concentration dependences of various magnitudes are shown. In luminescence, for example, a lifetime dependence on dopant concentration is often measured [1][2][3][4][5][6][7][8][9][10]. This dependence can be used for.…”

Growth optimisation of ZnS:Mn thin film phosphors for high intensity miniature electroluminescent displays

“…The optimum concentration reported in the literature varies with deposition technique and methods used to characterise, but is typically around 0.5 wt.% [9,10,11]. However some reports have indicated 'optimums' as high as 3 Mn mol% (1.5 wt.% ) [12] or as low as 0.2 wt.% [13].…”