凯发

Since the experimental isolation in 2004, graphene has attracted extensive attentions because of its unique properties.[1] Especially, graphene has been investigated widely for optoelectronic application. Due to low electron-phonon scattering, graphene has excellent transport properties with theoretical value of charge carrier mobility higher than 200, 000 cm2/V•s. A high transmittance of 97.7% per graphene layer is observed in visible light wavelength. Moreover, graphene presents outstanding mechanical robustness and chemical durability. The combination of these unique properties makes graphene an excellent candidate for application in optoelectronic devices, such as organic light-emitting diodes,[2,3] organic photovoltaic devices, [4] field emission devices,[5,6] and so on.  However, for practical applications, the graphenes synthesized by chemical vapor deposition (CVD) still show some critical drawbacks. For example, the sheet resistance of the CVD-grown graphenes is still much higher than the indium-tin-oxide (ITO) films. And, the 2D nature of the graphenes also limit their application in field emission devices. In this work, we developed a couple of hybrid nanocomposites based on graphene materials, and demonstrated their superior optoelectronic performances over pure graphenes.

We fabricated Graphene/Ag/Al-doped zinc oxide (AZO) multilayer films by using chemical vapor deposition and magnetron sputtering methods, as shown in Figure 1. The graphene/Ag/AZO film can maintain high conductivity and transmittance without obvious degradation during bending test. A green flexible organic light emitting diode with a structure of graphene/Ag/AZO/N,N- diphenyl-N,N-bis(1- napthyl)-1,1-biphenyl-4,4-diamine/tris(8-hydroxyquinoline) aluminum(III)/ lithium fluoride/Al exhibited a stable green emission and light-emitting efficiency during the cycle bending test.

Zinc oxide (ZnO) nanorods were vertically grown on the surface of graphene sheets by chemical vapor deposition, and their use in a field emission device was demonstrated, as shown in Figure 2. Using the graphene/ZnO nanorod hybrid structure, efficient field emission with low turn-on field, low threshold field, high emission spot density, high field enhancement factor and excellent emitting stability were obtained. It is proposed that the introduction of mid-density ZnO nanorods on the surface of graphene sheets can increase the number of emitters, enhance tunneling probability, and lead to optimized field emission for the hybrid emitters. The results showed that the field emission properties of graphene can be tailored by growing various ZnO nanostructures on its surface.

References:  

[1] A. K. Geim, K. S. Novoselov, Nat. Mater. 6 (2007)183. 

[2] Fushan Li, Zhixiao Lin, Beibei Zhang, Yongzhi Zhang, Chaoxing Wu, Tailiang Guo, Org. Elect. 14(2013)2139

[3] Xiaoxiao Wu, Fushan Li, Wei Wu, Tailiang Guo, Appl. Surf. Sci. 295(2014)214

[4] Fushan Li, Lijie Kou, Wei Chen, Chaoxing Wu, Tailiang Guo, NPG Asia Materials 5(2013)e60

[5] Chaoxing Wu, Fushan Li, Yongai Zhang, Tailiang Guo, Carbon 50(2012)3622

[6] Chaoxing Wu, Fushan Li, Yongai Zhang, Tailiang Guo, Bo Qu, Zhijian Chen, Appl. Surf. Sci. 257(2011)4539