Liu Xiaoliang, Wang Chenggong, Lyu Lu, Wang Congcong, Xiao Zhengguo, Bi Cheng, Huang Jinsong, Gao Yongli
Hunan Key Laboratory for Super-microstructure and Ultrafast Process, College of Physics and Electronics, Central South University, Changsha, 410083, P. R. China.
Phys Chem Chem Phys. 2015 Jan 14;17(2):896-902. doi: 10.1039/c4cp03842h. Epub 2014 Nov 18.
The electronic properties of interfaces formed between Au and organometal triiodide perovskite (CH3NH3PbI3) are investigated using ultraviolet photoemission spectroscopy (UPS), inverse photoemission spectroscopy (IPES) and X-ray photoemission spectroscopy (XPS). It is found that the CH3NH3PbI3 film coated onto the substrate of poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate) (PEDOT:PSS)/indium tin oxide (ITO) by a two-step method presents n-type semiconductor behavior, with a band gap of 1.7 eV and a valence band (VB) edge of 1.0 eV below the Fermi energy (EF). An interface dipole of 0.1 eV is observed at the CH3NH3PbI3/Au interface. The energy levels of CH3NH3PbI3 shift upward by ca. 0.4 eV with an Au coverage of 64 Å upon it, resulting in band bending, hence a built-in field in CH3NH3PbI3 that encourages hole transport to the interface. Hole accumulation occurs in the vicinity of the interface, facilitating the hole transfer from CH3NH3PbI3 to Au. Furthermore, the shift of the VB maximum of CH3NH3PbI3 toward the EF indicates a decrease of energy loss as holes transfer from CH3NH3PbI3 to Au.
利用紫外光电子能谱（UPS）、逆光电子能谱（IPES）和X射线光电子能谱（XPS）研究了金与有机金属三碘化物钙钛矿（CH3NH3PbI3）之间形成的界面的电子性质。结果发现，通过两步法涂覆在聚（3,4 - 乙撑二氧噻吩）聚（苯乙烯磺酸盐）（PEDOT:PSS）/氧化铟锡（ITO）衬底上的CH3NH3PbI3薄膜呈现n型半导体行为，带隙为1.7 eV，价带（VB）边缘比费米能（EF）低1.0 eV。在CH3NH3PbI3/Au界面观察到0.1 eV的界面偶极。当金覆盖层厚度为64 Å时，CH3NH3PbI3的能级向上移动约0.4 eV，导致能带弯曲，从而在CH3NH3PbI3中形成一个促进空穴向界面传输的内建电场。空穴在界面附近积累，促进了空穴从CH3NH3PbI3向金的转移。此外，CH3NH3PbI3价带最大值向EF的移动表明，当空穴从CH3NH3PbI3转移到金时，能量损失减小。
