LiBq_4/ITO和LiBq_4/CuPc/ITO表面的AFM与XPS分析

Surface analysis using AFM and XPS for LiBq_4/ITO and LiBq_4/CuPc/IITO

用 AFM 对蓝色 OLED 的空穴传输层 LiBq4/ITO 和 LiBq4/CuPc/ITO 表面扫描。结果均呈岛状结构。LiBq4沉积在 ITO 上成膜较差,在 CuPc 上成膜较好。说明加入 CuPc 能有效改善 LiBq4的成膜质量。XPS 对样品表面 In3d 和 Sn3d 的电子状态分析也证实 ITO 表面沉积 LiBq4膜存在裂缝,加入 CuPc 可抑制裂缝出现。分析指出,CuPc 由于 Cu(II)离子半满的 dx2-y2轨道在卟啉环平面内和氮强烈作用形成离域大π键,使 LiBq4的沉积状态改善。

The surfaces of the blue OLED with hole transmission layers LiBq4/ITO and LiBq4/CuPc/ITO are scanned by AFM. The results show that both layers represent island-like structure. The quality of LiBq4 film deposited on ITO is poor while that of LiBq4 film deposited on CuPc is good, which says that the sublimation of CuPc helps improve the quality of LiBq4 film. The analysis of surfaces of In3d and Sn3d specimens by XPS provides additional evidence that there exist some slits in the film of LiBq4 when directly being deposited onto ITO surface. The sublimation of CuPc on the surface of ITO can control the existence of slits. Moreover theoretical analysis shows that the strong interaction between partly full dx2-y2 orbits of the Cu(II) of CuPc in the plane of porphyrin ring and nitrogen atoms occurs to form layer-delocalized π bond which improves the quality of LiBq4 film deposited on CuPc.