Graphene has emerged as a promising material for photonic applications fuelled by its superior electronic and optical properties. However, the photoresponsivity is limited by the low absorption cross-section and ultrafast recombination rates of photoexcited carriers. Here we demonstrate a photoconductive gain of ~10⁵ electrons per photon in a carbon nanotube–graphene hybrid due to efficient photocarriers generation and transport within the nanostructure. A broadband photodetector (covering 400^-1,550 nm) based on such hybrid films is fabricated with a high photoresponsivity of >100 A W^-1 and a fast response time of ~100 μs. The combination of ultra-broad bandwidth, high responsivities and fast operating speeds affords new opportunities for facile and scalable fabrication of all-carbon optoelectronic devices.

Nature Communications 6, Article number: 8589 doi:10.1038/ncomms9589
Received 22 March 2015 Accepted 09 September 2015 Published 08 October 2015

http://www.nature.com/ncomms/2015/151008/ncomms9589/full/ncomms9589.html

最近，南京大学电子科学与工程学院王枫秋教授、徐永兵教授、张荣教授带领的研发团队在新型低维材料光探测器研究领域取得重要进展，相关论文于2015年10月8日在线发表于《Nature communications》杂志。

石墨烯是零带隙的二维材料，高载流子迁移率及宽带光响应等特性使其成为高性能光探测器的理想材料之一。然而，单层石墨烯较低的吸光率和超快的光生载流子复合过程，严重制约了器件的光响应度。课题组从全碳复合材料界面处丰富的调控自由度和高效的电子迁移出发，提出将一维的碳纳米管和二维石墨烯结合形成 "原子层厚"薄膜，将有可能大幅提高器件的工作性能。

基于该新型全碳复合薄膜高迁移率、宽谱光吸收以及可大面积制备等特性，研究团队首次实现了基于单壁碳管-石墨烯复合薄膜的光探测晶体管。表征显示，该新型器件可在整个可见光－近红外波段工作（400-1550 nm），光响应度大于100 A/W。更令人惊奇的是，由于全碳界面处的范德华互作用，器件响应速度达100 μs，比石墨烯-量子点复合体系的响应速度提高了三个数量级左右，展示了优异的综合性能和实用化前景。此外，该研究也首次将基于二维材料的范德瓦尔斯异质结（van der Waals heterostructures）扩展到了一维/二维复合结构。为研究范德华异质结中基于量子局限效应的新奇物理现象提供了一个全新的平台。基于这项发现，课题组已经申请国家发明专利一项，并已进入实审阶段。