De-Excitation Processes and Efficiency in ALE ZnS: Mn Thin Film Electroluminescent Devices

Abstract

The decay curves of the emission due to the radiative de‐excitation of Mn2+ in ZnS: Mn ALE. electroluminescent (EL) devices are well described by considering two non‐radiative processes: a diffusion‐limited relaxation and interactions between excited Mn* ions. These processes are evaluated according to the Mn concentration, the interfaces, and the emitted light level. The internal efficiency curves are drawn versus the Mn concentration and it is shown that the optimal concentration is a function of the brightness level.

Improved electroluminescence of ZnS:Mn thin films by codoping with potassium chloride

“…The photoluminescent decay of Mn is shown in Fig. 6 and can be fit by an exponential to the nth power, similar to the decay behavior reported by Benoit et al 11 for higher Mn concentrations such as are used for EL devices. The decay behavior was not changed by codoping ZnS:Mn with KCl ͓compare Fig.…”

Photoluminescence Behavior of Manganese‐Doped Zinc Silicate Phosphors

“…Moreover, there should be more complications by considering the fact that cross relaxation also occurs. 13,14 On the other hand, trap-involved processes, which can retard the overall decay process, occur to a certain extent when excited in the UV range above E T . [15][16][17] Even if the trap-involved charge transfer between the host and the Mn ions were a controlling step, the shortening of the decay time with increasing manganese content could be interpreted in terms of a trapinvolved model, 9 where it is assumed that the rate-controlling step for manganese emission could be recombination between the trapped electrons and the Mn ions that have been ionized through either thermal emission or tunneling.…”

“…Such a difference might be related to the complexity of interaction behavior between Mn centers that include cross relaxation. 13,14 The lifetime in this range can be expected to decrease, in comparison to ranges II or III, by considering the fact that no trap-involved process occurs. However, in actuality, the difference is not great between ranges I and II, as far as the near-resonant ( 4 T 1 level) excitation is concerned, even if range I shows a slightly shorter lifetime than the others.…”