Research On Interface Structures At Transitional Metal Oxides On Organic Semiconductors

Organic light emitting diodes(OLEDs)have attracted a broad attention in academia and industry as a new generation of lighting and display technology.The deposition sequence of Molybdenum oxide(Mo O₃)has a great impact on the performance of the device.Compared with conventional structures(e.g.,organic semiconductor deposition on the Mo O₃),the inverted structure can be better integrated with the circuit driver panel,effectively improving the aperture ratio,luminescent efficiency and service life of the device,so the electronic characteristics at its interface are particularly important.This thesis mainly focuses on the interface formed by Mo O₃deposition on organic semiconductors.It is proposed that a physical cleavage method to obtain the buried interface,and the interface is systematically studied by photoelectron spectroscopy combined with depth sputtering profiles.Detail works in this thesis are as follows:(1)The interfacial formation of Mo O₃ on organic semiconductors with different molar masses is studied.The sample structure is as follows:Si/Organics/Mo O₃/Ag,organic molecular materials including TCTA?NPB?CBP and m CP,respectively.It is found that there are two distinct types of interfaces:sharp interface(type-I)where Mo O₃ has limited or no diffusion upon deposited on organics such as TCTA and NPB;mixed interface(type-II)where the formation of interfaces(e.g.,Mo O₃/CBP and Mo O₃/m CP)is followed by significant diffusion and reaction.The diffusion of Mo O₃is inversely proportional to the molar mass of organic molecules on the substrate.In high-resolution spectra of Mo 3d and C 1s,we detected new chemical states,Mo^x+and C^x+,which is the result of charge transfer at the interface.(2)The effect of Mo O₃ deposition rate on the interface structure was studied.Samples structure with Si/NPB/Mo O₃/Ag were prepared with Mo O₃ deposition rates of 0.1(?)/s,0.5(?)/s and 1(?)/s,respectively.It is found that the deposition rate of Mo O₃will affect the interfacial structure,the faster deposition rate,the lower amount of Mo O₃diffusion into organic molecules.The results of photoelectron spectroscopy and depth sputtering profiles show that the cleavage method for obtaining the buried Mo O₃/organic semiconductor interface structure is perfectly reproducible,and it is easy to implement This technique provides a new research method for future interface characteristics.