ZnS:Mn,Cu粉末p-V-n结直流电致发光

对ZnS:Mn,Cu粉末DCEL屏的形成过程及光电特性作了研究.观测到经形成的EL屏具有整流特性及相位开关效应,发光局限于阳极附近,EL屏具有光生伏特效应.随着形成电压的提高与形成时间的延续,EL屏的电容量由大变小,局部发光区(结区)也从阳极附近向体内迁移.上述实验结果表明:经形成EL屏的阳极附近存在势垒-CuxS-ZnS:Mn,Cu异质结.文中采用p-v-n结模型分析发光屏的导电机构及激发机制,指出发光区的迁移是EL屏退化的重要因素之一.采用正弦电压(频率20Hz—20kHz)激励,观测EL屏的形成过程.初步认为,EL屏的形成与老化过程主要由热引起.因此,制备具有高度热稳定性的包铜ZnS粉末屏是十分重要的.

DC ELECTROLUMINESCENCE IN ZnS:Mn,Cu POWDER PHOSPHORS WITH p-v-n JUNCTIONS

In this paper,the behaviour of forming process and the electrical and optical properties in direct current electroluminescent(DCEL)ZnS:Mn,Cu powder panels are presented.By using static and dynamic methods to measure the current-voltage(i~V)characteristic curves of newly-formed panels,it was found that,the curves exhibit a rectifying behaviour and a phase modulation effect(asymmetry in phaseshift),and the luminescent region is localized in adjacent to the anode.In order to further examine whether a barrier is existed in the formed panel,the anode and cathode surface is illuminated by light respectively.Thereis a photovoltaic effect when the anode is illuminated,but not when the cathode is.By inference from this effect,it seems probable that a CuxS-ZnS barrier would be created near the anode of the formed panel.Increasing the forming voltage or prolonging the forming time,the capacitance of the panel decreases and the luminescent region migrates gradually out from the anode into the phosphor layer.At last,the light transmitted from the cathode surface becomes much more intense than that from the anode surface.This fact of migration of luminescent region would be one of the significant factors which cause the panels to age.To analyse the electrical conduction and excitation mechanisms of the panels a p-v-n junction model is proposed.By using the equivalent circuit and simplifying the calculations,the model is able to explain the results obtained by Alder et al.,i.e.,the asymmetry in the i~V characteristics increases with increasing forming voltage;the reciprocal capacitances are linear with the forming voltages for both forward and backward voltage;the lines with different slopes do not pass through the origin of the 1/c~V diagram.Also investigated was the forming process under sinusoidal,20-20kHz source.For gap type devices,several adjacent luminescent regions exist simultaneously even in a gap,and the luminescent regions are nonuniform in shape.Although there are in practice so many factors that may contribute to the forming and aging processes and thus there is at present no common agreement on the processes,we rather consider that the overheating of the phosphor layer is a most important factor inducing the forming and aging processes.