CuPc/ITO结构的表面和界面电子态的XPS研究

覆盖有Indium tin oxide(ITO)膜的透明导电玻璃广泛地用作有机发光器件 (OLEDs)的空穴注入电极 ,但是ITO膜的功函数通常与空穴传输材料的最高被占据分子轨道 (HOMO)不匹配。铜酞菁 (CuPc)作为缓冲层可以提高空穴从ITO向空穴传输材料的注入效率。对CuPc ITO样品的XPS表面分析表明 ,在CuPc分子中 ,铜原子显 2价 ,通过配位键和氮原子相互作用。CuPc分子中有两类碳原子 :8个C原子与 2个N原子成键 ;其余 2 4个C原子具有芳香烃性质。N原子也处在两种化学环境中 :有 4个N原子只与 2个C原子形成CNC键 ;另外 4个N原子不仅与 2个C原子成键 ,还通过配位键与Cu原子成键。用氩离子束对样品表面进行了溅射剥蚀 ,当溅射时间分别为 2 ,5 ,10min时进行XPS采谱分析 ,结果表明 ,随着氩离子束溅射时间增长 ,C 1s,N 1s峰变弱 ,Cu 2p ,O 1s,In 3d,Sn 3d峰增强 ,C 1s,N 1s,O 1s,In 3d和Sn 3d峰都向高束缚能或低束缚能方向移动 ,但它们的情况却不相同。

Surface and Interface Analysis for Copper Phthalocyanine (CuPc) and Indium-Tin-Oxide (ITO) Using X-Ray Photoelectron Spectroscopy (XPS)

Indium-tin-oxide (ITO) coated glass has been widely used as a hole injection electrode for organic light-emitting devices (OLEDs), but the work function of ITO film usually mismatches the highest occupied molecular orbital (HOMO) of the hole transport materials. Copper phthalocyanine (CuPc) has been used as a hole injection buffer to enhance the hole injection from ITO to the hole transport layer. A thin CuPc layer was thermally evaporated onto the ITO-coated glass substrate, and the surface and interface electron states of the CuPc/ITO close contact were measured and analyzed by X-ray photoelectron spectroscopy (XPS) technology. Results show that, in CuPc molecule, copper atom has a valence of 2 and interacts with nitrogen atoms through coordinate bonds. There are two kinds of carbon atoms: eight carbon atoms bonding with two nitrogen atoms and other 24 carbon atoms with an aromatic hydrocarbon character. The nitrogen atoms are also in two kinds of chemical environment: four nitrogen atoms only bond with two carbon atoms forming CNZJLX,Y]C bonds, and other four nitrogen atoms not only bond with carbon atoms but also bond with copper atom through coordinate bonds. Argon ion beam sputtering was used to study the interface characteristics of the CuPc/ITO contact. As sputtering time increases, the peaks of C 1s and N 1s spectra gradually become weaker, the peaks of Cu 2p, O 1s, In 3d and Sn 3d spectra get stronger. The core-levels of C 1s, N 1s, O 1s, In 3d and Sn 3d spectra all have chemical shifts towards higher or lower binding energy, but their behavior are different.