基于特种有机酸盐p型重掺杂石墨烯透明导电薄膜的构筑及特性

Graphene, a new generation of transparent conductive film (TCF), has a great potential for a wide range of applications in future flexible optoelectronic devices，owing to its distinctive structure and outstanding properties. However, the relatively high sheet resistance, and low work function significantly limit the application of graphene TCFs (G-TCFs) in optoelectronic devices. In this application, we propose a new idea to simultaneously solve the above problems by building stable and controllable heavily doped p-type (i.e. p+-type) G-TCFs with excellent comprehensive performance using particular organic acid salts, such as iron (III) trifluoromethanesulfonate (C3FeF9O9S3), etc. as p-type dopants because they have multiple strong electron-withdrawing groups, outstanding thermal and chemical stability, and good film forming ability at low temperature. First principles calculations were performed to evaluate the interactions of organic acid salts dopants with graphene as well as the carrier transport properties of p+-type doped graphene. Furthermore, the influences of p+-type doping on structure and properties of graphene, including transmittance, conductivity, and work function, will be investigated to elucidate the mechanism of stable and controllable p+-type doping effect. Based on above results, we will establish the relationship between the organic acid salts dopants and structure and properties of as-doped graphene, and fabricate G-TCFs with excellent comprehensive performance, which will be used as anode of organic light-emitting diode (OLED) to prove their advantages as the transparent electrode of high-performance optoelectronic devices. This study will paves the way for the application of high-performance G-TCFs in next generation flexible and wearable optoelectronic devices.

石墨烯具有独特的结构和优异的性能，作为新一代透明导电薄膜在未来的柔性光电器件中具有广阔的应用前景。然而，较高的面电阻和较低的功函数严重制约了石墨烯在光电器件中的应用，针对这一“瓶颈”问题，本项目提出采用具有多种强吸电子基团的特种有机酸盐作为p型掺杂剂，利用蒸发镀膜的均匀性和易控性、特种有机酸盐良好的热稳定性、化学稳定性和低温成膜性，实现石墨烯稳定、可控p型重掺杂，提高其综合性能。第一性原理计算与实验结合研究特种有机酸盐与石墨烯之间的相互作用，掺杂石墨烯的载流子输运特性以及掺杂对石墨烯薄膜结构、透光性、导电性和功函数的影响，阐明以特种有机酸盐作为掺杂剂实现石墨烯稳定、可控p型重掺杂的机理，建立特种有机酸盐掺杂方法-石墨烯薄膜结构与性能关系，制备大面积综合性能优异的石墨烯透明导电薄膜，并探索其在有机发光二极管（OLED）中的应用，为实现石墨烯透明导电薄膜在柔性光电器件领域中的广泛应用奠定基础。

石墨烯透明导电薄膜（TCF）相对较高的面电阻、较低的功函数及较大的表面粗糙度等问题严重制约了其在光电器件中的应用。本项目提出了采用具有多种强吸电子基团的双三氟甲烷磺酰亚胺锂盐作为p型掺杂剂；利用双三氟甲烷磺酰亚胺锂盐良好的热稳定性、化学稳定性，实现石墨烯薄膜的均匀、稳定和可控p型重掺杂，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CVD石墨烯无介质转移方法，通过原位掺杂手段直接构筑p型重掺杂石墨烯/石墨烯异质结。与原始的5层石墨烯相比，导电性和功函数明显提高，透光率和表面粗糙度无明显变化。以p型重掺杂石墨烯/石墨烯TCF作为阳极，制备了绿光柔性有机发光二极管（OLEDs），最大电流和功率效率分别达到了78 cd A-1 and 74 lm W-1，效率均高于ITO和本征石墨烯TCF的结果。同时，发展了一种石墨烯/PEDOT:PSS复合TCF，以这种表面洁净、粗糙度极低的TCF作为阳极，在国际上首次制备出发光面积为2.5英寸的石墨烯基绿光柔性OLED原型器件，其亮度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。石墨烯基TCF优异的综合性能有望促进石墨烯在未来高性能柔性和可穿戴光电器件中的广泛应用。