Developments and Application of Multicolor Thin Film EL Devices

The electroluminescent characteristics of ac-driven think -film electroluminescent devices werestudied. These devices were proposed and developed by the head investigatiorand differed from usual devices in the structure of the active layer, i.e.，additional intermediate layer ("gate layer") was buried in ZnS active layers. Thus，devices strucure is a glass substrate：electrode <I> (< sno_x >)-insulator <I> (< y_2 > < o_3 >)-active layer <I> (impurity doped ZnS)-gatelayer-active layer <II> (impurity doped ZnS)-insulatalor <II> (< y_2 > < o_3 >)-electrode <II>（Al）.The results of The investigation are as follows.(1). The emission color of The device was ableto be continuously varied between the emission color of the active layer <I> and that of <II> by thedriving voltage and frequencyonly when the gate layer thickness was in the optimum range which was dependent on its material(2)。The optimum range of a gate layer thickness was 10 - 60 <Ang> in The case of a metal gate，and 500 -1000 <Ang> of an insulator gate In the case of a semiconductor gate it was wideconsiderably, for example, it was 200 - 3000 <Ang> when a门层material was < wo_3 > . Further，这不是在积极主动层层或在积极主动层层层的一种kind of impurity doped in the active(3). The tendencies of The dependency of emisson color on The driving conditions weredifferent according to gate materials.这些被应用于两个类别，4 . emisson color的变化是在低的基础上形成的。temperature (approx. - 100c). The electroluminescent spectrum of an active layer, however，已经改变了low temperatuere depending on a kind of an impurity. This phenomenon had nothing todo with the existence of a gate layer.(5) It was considered that the changeablity of the emission这些设备的颜色是due to the accumulation and the emission of electrons at the gate layer。

The electroluminescent characteristics of ac-driven thin-film electroluminescent devices were studied. These devices were proposed and developed by the head investigatior, and differed from usual devices in the structure of the active layer, i.e., the additional intermediate layer ("gate layer") was buried in ZnS active layers. Thus, the strucure of devices is a glass substrate: electrode <I> ( <SnO_x> )-insulator <I> ( <Y_2> <O_3> )-active layer <I> (impurity doped ZnS)-gate layer-active layer <II> (impurity doped ZnS)-insulatalor <II> ( <Y_2> <O_3> )-electrode <II> (Al).The results of the investigation are as follows.(1). The emission color of the device was able to be continuously varied between the emission color of the active layer <I> and that of <II> by the driving voltage and frequency, only when the gate layer thickness was in the optimum range which was dependent on its material.(2). The optimum range of a gate layer thickness was 10 - 60 <Ang> in the case of a metal gate, and 500 -1000 <Ang> of an insulator gate. In the case of a semiconductor gate it was wide considerably, for example, it was 200 - 3000 <Ang> when a gate layer material was <WO_3> . Further, it was not dependent on the thickness of each active layer or a kind of impurity doped in the active layer.(3). The tendencies of the dependency of emisson color on the driving conditions were different according to gate materials. These were approximately grouped into two classes, and were contrary with each other.(4). The changeablity of the emisson color was maintained at low temperature (approx. -100゜C). The electroluminescent spectrum of an active layer, however, was changed at low temperatuere depending on a kind of an impurity. This phenomenon had nothing to do with the existence of a gate layer.(5). It was considered that the changeablity of the emission color of these devices was due to the accumulation and the emission of electrons at the gate layer.