直流电致发光(DCEL)器件在交流(AC)电压下的I-V,B-V和B-I特性

CURRENT -VOLTAGE(I-V), BRIGHTNESS -VOLTAGE(B-V) AND BRIGHTNESS-CURRENT (B-I) CHARACTERISTICS OF DIRECT-CURRENT ELECTROLUMINESCENT(DCEL)DEVICES UNDER ALTERNATING-CURRENT(AC)VOLTAGE OPERATION

本文研究了DCEL器件在AC条件下的电流—电压(I—V),亮度—电压(B—V)和亮度—电流(B—I)特性.提出了在不同激发条件下的I—V,B—V和B—I的经验公式.证明了DCEL器件在AC条件下按激发条件可分为三个负载区:容性负载区,电阻负载区和混合负载区.在不同的负载区DCEL器件呈现完全不同的光电特性.证明了在不同负载区工作时磷光粉层内电场分布和电子能量分布截然不同.分析了上述特性的原因.证明了老化和形成过程具有同样的物理机制,老化是形成过程的继续.

ZnS:Mn, Cu powder direct-current electroluminescent( DCEL) devices show wonderful characteristics under alternating-current (AC) voltage operation. The brightness of several tens of foot-1ambert can be obtained easily at no V and 50 Hz, which is two orders of magnitude brighter than that of conventional ZnS:Cu, C1 powder ACEL devices under the same circumstances.This signifies a great achievement in the field of ACEL phosphors.This paper reports the dependences of current-voltage(I-V), brightness-voltage (B-V) and brightness-current (B^I) of DCEL devices as a new kind of ACEL devices. The empirical formulae of above dependences are presented. On the basis of the experimental results, it is confirmed that there are three areas for the load of DCEL devices at AC operation depending on excited conditions. In higher voltage and lower frequency area, DCEL device appears to be a resistive load; in lower voltage and higher frequency area, it appears to be a capacitive load,and between the above mentioned areas, it appears to be a mixed load. The extent of the voltage and frequency for each load area depends on the forming and aging processes. The further forming and aging result in the enhancement of properties of capacitive load and the expansion of all of load areas into high voltage and low frequency area.DCEL devices in the three load areas have different characteristics. In the area of capacitive load, I-V , B-V and B-I dependences are given as follows:And in the area of resistive load above dependences can be written asin which I0,I01,B0,B0' and B0' are constants, n= 6 - 7 .The quantum efficiency is discussed in various load areas. Analysing the experimental results it is indicated that the quantum efficiency is much lower in the area of capacitive load than that in the area of resistive load. But its raise with increased the current with a high rate is super-linear. In the area of resistive load, the qnantum efficiency goes to the highest and then keeps constant with the increased current. This suggests that in area of the resistive load, the distribution of electron in energy should not be changed with the increaed current, and the field strength in emmitting layer should be as well and come to the top. It is also concluded from the result of quantum efficiency that DCEL devices operated in the area of resistive load comprise much more high-energy electrons in its excitation current than in the area of capacitive load. The distinctions are explained.It is exposed that the forming and aging processes result in uniform effects in the ACEL characteristics of DCEL devices. Therefore, it is considered that the forming and aging processes have the same mechanism and the aging resulting from Cu+ migration is just like the forming process,