氧化石墨烯/石墨烯叠层异质结构透明导电薄膜的构筑与性能

The relatively high sheet resistance, low work function, and poor compatibility with other functional layers significantly limit the application of graphene transparent conductive films (TCFs) in opto-electronic devices. In this application, we propose a new idea to simultaneously solve the above problems by constructing graphene oxide/graphene (GO/G) stacked heterostructure because GO has good hydrophilicity and high work function, and can be used as a p-dopant for graphene with high stability. An etching-free ozone treatment will be developed to prepare GO/G films by directly oxidizing the top layer of multi-layer graphene films because graphene can be oxidized without destroying its basal plane structure at low temperature and atmospheric pressure, a gas-solid reaction prefers to occur on the surface, and perfect graphene is impermeable to all gases. Furthermore, the relationship between structure and properties of GO/G stacked heterostructure films, including conductivity, transmittance, work function and wettability, will be investigated to elucidate the effect of GO on improvement of the performance of the graphene TCFs. Based on above results, we will obtain GO/G stacked heterostructure TCFs with excellent comprehensive performance, which will be used as anode of organic light-emitting diode to prove their advantages as the transparent electrode of high-performance opto-electronic devices. This study will provide fundamentals for the application of high-performance graphene-based TCFs in next generation flexible and wearable opto-electronic devices.

为解决电阻高、功函数低、表面不润湿等制约石墨烯透明导电薄膜在光电器件中应用的“瓶颈”问题，本项目提出利用氧化石墨烯（GO）具有较好浸润性、较高功函数以及对石墨烯（G）的稳定掺杂作用，构筑GO/G叠层异质结构，提高透明导电薄膜的综合性能。利用臭氧在低温常压下可氧化石墨烯、“气－固”反应通常在固相表面发生以及石墨烯防气体渗透的特点，建立臭氧选择性氧化多层石墨烯顶层直接构筑GO/G叠层异质结构薄膜的方法。研究GO/G叠层薄膜结构与其导电性、透光性、功函数和表面润湿性能的关系，阐明GO改善石墨烯透明导电薄膜性能的作用原理，制备综合性能优异的GO/G叠层异质结构透明导电薄膜，探索其在有机发光二极管中的应用，为促进石墨烯透明导电薄膜在光电器件领域中的应用奠定基础。

石墨烯透明导电薄膜（TCF）相对较高的电阻、较低的功函数及较差的界面相容性等问题制约了其在光电器件中的应用。本项目提出了利用氧化石墨烯（GO）具有较好浸润性、较高功函数以及对石墨烯（G）的稳定掺杂作用，构筑GO/G叠层异质结构，提高石墨烯TCF的综合性能，进而探索其在柔性光电器件中的应用。发展了臭氧处理的方法，通过选择性氧化多层石墨烯顶层直接构筑了GO/G叠层异质结。所得GO/G/G TCF相比于原始的三层石墨烯，透光性和功函数明显提高。虽然导电性没有变化，但与原始的两层石墨烯相比，电阻大大降低。而且，GO/G TCF浸润性也得到了明显的改善，可以在其表面获得非常均匀平整的MoO3空穴注入层。以GO/G TCF作为阳极，组装了红、绿、蓝、白等多种颜色的柔性有机发光二极管（OLED），效率均高于ITO和石墨烯TCF的结果。其中，绿光器件的最大电流和功率效率分别达到了82.0 cd A-1 和98.2 lm W-1，比石墨烯器件分别高出了36.7% 和59.2%，比ITO器件分别高了14.8%和15.0%，是已报道的石墨烯基OLED中最好的结果之一。同时，发展了一种以小分子松香作为转移介质的方法，实现了大面积石墨烯的洁净、无损转移。以这种表面洁净、粗糙度极低的石墨烯构建的GO/G TCF作为阳极，在国际上首次制备出发光面积为4英寸的石墨烯基柔性OLED原型器件，较文献报道的有效发光面积提高了近2个数量级，亮度高达10, 000 cd m-2，已达到照明和显示的实用要求，并且数次弯折后性能不衰减。此外，以GO/G TCF为阳极，制备出了光电转化效率高达5.8%的柔性有机太阳能电池。GO/G TCF优异的综合性能有望促进石墨烯在下一代高性能柔性和可穿戴光电器件中的广泛应用。