NPB/Alq_3双层有机电致发光器件薄膜厚度与器件性能的优化

Study of the Effect of Film Thickness on the Performance of NPB/AIq_3 Double Layer Organic Light-Emitting Diodes

研究了以NPB为空穴传输层、Al_(q3)为发光层的双层异质结有机电致发光器件的薄膜厚度对器件性能的影响.制备了一系列具有不同NPB和Al_(q3)厚度的器件并测试了其电致发光特性.结果表明,器件电流随Al_(q3)与NPB厚度变化的关系并不相同.不同有机层厚度双层器件的电流机制符合陷阱电荷限制(TCL)理论,随外加电压的增大,器件电流经历了欧姆电导区、TCL电流区、陷阱电荷限制.空间电荷限制(TCL-SCL)过渡区三个区域的变化.当有机层厚度匹配为NPB(20nm)/Al_(q3)(50nm)时可以获得性能优良的器件.器件的流明效率-电压关系曲线的变化规律是在低电压区较快达到最大值,然后随电压的增加逐渐降低.

We studied the effect of thin film thickness on the performance of double-layer heterojunction organic light-emitting diodes（OLEDs）based on 4,4＇-bis[N-1-napthyl-N-phenyl-amino]biphenyl（NPB）as hole transporting layer and iris-（8-hydroxylquinoline）-aluminum（Alq3）as emitting layer.Various devices with different NPB and Alq3 thickness were fabricated and their electroluminescent characteristics were investiagted.The results show that the device current dosen＇t change with Alq3 or NPB film thickness in the same trend.The current mechanism of devices with different organic film thicknesses conforms with the theory of trapped charge limited current（TCLC）.Current varies from ohmic conduction region,TCL region to trapped charge limited-space charge limited（TCLC-SCLC）transition region with the increase of applied voltage.High device performance could be obtained when thin film thickness is NPB（20nm）/Alq3（50nm）.The luminance efficiency-voltage curves of devices reached to the maximum under low-voltage,and gradually decreased with rising voltage.