绝缘衬底上石墨烯的PECVD低温制备、多维结构调控及其光电应用

Graphene has widely potential applications due to outstanding optical and electrical properties, but the preparation of high-quality graphene by chemical vapor deposition (CVD) method generally involves in both high reaction temperature and complex transfer procedure. Therefore, direct low-temperature growth of graphene on dielectric substrates is the key to its optoelectronic applications. The project intends the development of plasma-enhanced CVD to prepare 2D/3D graphene and multi-dimensional structure on dielectric substrates at low temperature, carries out in-situ composites of graphene and semiconductor materials, and fabricates novel concept graphene-based prototype device. Firstly, studying the effects of experimental parameters such as growth temperature, precursor, work pressure,etc., analyzing the intrinsic relationship between structure and properties of graphene, and revealing the growth mechanism; Secondly, controlling surface characteristics and photoelectric properties of graphene by the use of chemical doping and chemically modification; Thirdly, exploring the preparation methods of semiconductor materials such as TiO2, NiS, etc., on the graphene surface, and studying the interface bonding, electron transport and photoelectric response characteristics of graphene/semiconductor materials; Finally, assembling new structure optoelectronic devices based on graphene/semiconductor materials as the photoanodes and counter electrodes, optimizing the band structure and work function match, and obtaining new concept prototype device based on graphene multi-dimensional structure.

石墨烯因其优异的光电性能而有广阔的应用前景。高质量石墨烯采用化学气相沉积（CVD）法制备，通常需要高温反应和繁琐转移的工序。因而，直接在绝缘衬底上低温生长石墨烯是其光电应用的关键。本项目拟发展等离子体增强CVD法在绝缘衬底上低温制备2D/3D石墨烯以及多维结构，开展石墨烯与半导体材料的原位复合，并应用于石墨烯基新概念原型器件。首先，研究生长温度、前驱物引入量和工作气压等参数对石墨烯生长的影响规律，分析石墨烯结构和性能间的内在关系，揭示生长机理；其次，利用化学掺杂和化学修饰调控石墨烯表面性质和光电性能；再次，探索石墨烯表面诱导生长TiO2和NiS等半导体材料的制备方法，研究石墨烯/半导体材料的界面键合、电子输运和光电响应特性等；最后，将石墨烯/半导体材料复合结构作为光阳极和对电极组装新型结构光电器件，优化器件中能带结构和功函数匹配性，集成出基于多维石墨烯结构的新型原型器件。

本项目重点探索了等离子体增强化学气相沉积（PECVD）法在绝缘衬底上生长石墨烯导电薄膜，调控石墨烯的微观结构，构建石墨烯复合电极材料，应用到新概念太阳电池上。具体研究成果如下：（1）开发PECVD法在绝缘衬底上低温制备石墨烯的新工艺，获得二维石墨烯透明导电薄膜，其微结构为由直立的石墨纳米墙组成的连续的花瓣状三维网络结构。在350~2000 nm透过率>87.6%，方块电阻996 ohm/sq.，透过率为38%时，方块电阻仅为198 ohm/sq.，优于GO还原制备的石墨烯薄膜和直接使用低压CVD在SiO2衬底上生长的石墨烯薄膜。制备的石墨烯透明导电薄膜可以作为很好地透明电极替代TCO作为前电极，同时，作为染料敏化电池的背电极，其效率与传统昂贵的FTO的电池效率相当。（2）利用低温溶液法在绝缘玻璃衬底上生长了高导电性的硫化镍纳米线阵列薄膜，用作染料敏化太阳电池的对电极，得到了与常规Pt/FTO对电极相当的电池转换效率，可同时取代导电TCO衬底及贵金属Pt催化剂。（3）在绝缘衬底上直接生长高导电的石墨烯薄膜，该石墨烯结构具有优异的电学性能，方块电阻可达8 ohm/sq.，在其表面生长三维结构的石墨烯纳米墙、石墨烯纳米球，作为支撑体/导电基底，与电催化材料（硫化镍、硫化钴、硫化钨和硫化钼等）复合，制备出高效的FTO-free和Pt-free对电极，电池效率高于传统的Pt/FTO对电极的性能。（4）利用多孔陶瓷衬底作为模板，构筑出三维石墨烯管宏观体材料，该石墨烯宏观体由石墨烯纳米管组成，石墨烯管间共价键连接具有高强度、超高弹性和优异的电导率，其力学和电学性能是目前报道的多孔石墨烯的1-2个数量级高。多孔石墨烯材料具有超疏水特性，吸附有机溶剂超快，吸附有机溶剂达自身重量的600倍以上，电化学性能优异。