FePc与TiO2(110)及C60界面电子结构研究

基于C₆₀受体和有机分子给体的太阳能电池是目前非常重要的一个研究热点, 利用同步辐射真空紫外光电子能谱(SRUPS) 技术研究了酞菁铁(FePc)与TiO₂(110)及C₆₀的界面电子结构, 以及FePc与C₆₀分子混合薄膜的电子结构. SRUPS价带谱显示, FePc沉积在化学计量比与还原态两种不同的TiO₂(110)表面时, FePc分子的HOMO能级均随FePc厚度的变化发生了移动, 而在化学计量比的TiO₂(110)表面位移较大, 同时发生界面能带弯曲, 说明存在从有机层向衬底的电子转移. 在FePc/C₆₀和C₆₀/FePc界面形成过程中, FePc与C₆₀分子的最高占据分子轨道(HOMO)位移大小基本相同. 由界面能级排列发现, 在FePc与C₆₀的混合薄膜中, FePc分子的HOMO与C₆₀分子的最高占据分子轨道能级差较大, 这有利于提高器件开路电压, 改善器件性能.

The interfacial electronic structures at FePc/TiO2(110) and FePc/C60 interface

The electronic structures at the interfaces of iron phthalocyanine (FePc)/TiO₂(110), FePc/C₆₀ and FePc:C₆₀ blends are studied in situ by synchrotron radiation-based ultraviolet photoelectron spectroscopy (SRUPS). It is found that the interaction between organic molecules and the surface of reduced rutile TiO₂(110) is stronger than that of the stoichiometric TiO₂(110) interface. The energy level alignments at the FePc/C₆₀ interface and FePc:C₆₀ blends are drawn based on the evolutions of the interfacial electronic structures. From the SRUPS spectra, the band bending energies are found to be 0.45 eV in the C₆₀ layer and 0.1 eV in the FePc layer at the FePc/C₆₀ interface. The interface dipole energy is 0.2 eV at the FePc/C₆₀ interface. The offsets between the HOMO of FePc and LUMO of C₆₀ are 0.85 eV at FePc/C₆₀ and 1.04 eV at FePc:C₆₀ blends, which indicates that the blend films can improve the efficiency of the relevant optical-electric devices.