Sehrawat Poonam, Julien C M, Islam S S
Centre for Nanoscience and Nanotechnology, Jamia Millia Islamia (A Central University), New Delhi 110025, India.
Institut de Minéralogie, de Physique des Matériaux et de Cosmochimie (IMPMC), Sorbonne Université, CNRS-UMR 7590, 4 place Jussieu, 75252 Paris, France.
ACS Appl Mater Interfaces. 2020 Sep 2;12(35):39730-39744. doi: 10.1021/acsami.0c08028. Epub 2020 Aug 18.
We document the fabrication and investigations of a novel photodetector based on a WS quantum dots and reduced graphene oxide (RGO) (WS-QDs/RGO) heterostructure. The proposed photodetector is simple, scalable, cost-effective, and flexible and works in an ambient environment. An enhanced photodetection efficiency is observed due to the superior electronic properties of WS-QDs and excellent electrical as well as thermal properties of the carrier transportation medium, RGO. For device fabrication, GO and WS-QDs were separately synthesized via different chemistry followed by decorating WS-QDs on RGO coated cotton textile. Characterization studies confirm the transformation of exfoliated WS-2D flakes into WS-0D quantum dots and graphene oxide (GO) to RGO. The optimized photodetection performance of WS-QDs/RGO demonstrates its photoresponsivity of 5.22 mA W at 1.4 mW mm power density of a 405 nm illumination source. Other sensor parameters such as photosensitivity (∼20.2%), resolution (∼0.031 mW mm μA), response time (1.57 s), recovery time (1.83 s), and specific detectivity (∼1.6 × 10 jones) are found for WS-QDs/RGO sensor, and a few of these parameters are comparable and even superior to some of the devices as reported. Photosensing mechanism is explained in terms of charge transfer caused by appropriate band alignment across the interface between WS-QDs and RGO, where dimensionality and quantum confinement of nanostructures synergistically enhance the overall performance of the heterostructure. The device flexibility is examined through bending, stretching, and twisting experiments and successfully demonstrated its potentiality. Sensor performance even after being soaked in water and subsequent drying shows the possibility of reuse. The attributes of flexibility, high sensitivity and responsivity, superior resolution, and cost-effectiveness of our novel flexible photodetector indicate its promising potential for flexible and wearable optical detectors operating in UV band. Although negative photoconductance of the WS-QDs/RGO sensor is a major cause for not allowing the sensor to show its best performance, a trade-off is made with improved device design to qualify the expectations of being a competitive device, and this has been demonstrated with experimental facts.
我们记录了一种基于WS量子点和还原氧化石墨烯（RGO）（WS-QDs/RGO）异质结构的新型光电探测器的制备及研究情况。所提出的光电探测器结构简单、可扩展、具有成本效益且灵活，可在环境条件下工作。由于WS量子点优异的电子特性以及载流子传输介质RGO出色的电学和热学特性，观察到了增强的光电探测效率。在器件制备过程中，分别通过不同化学方法合成了氧化石墨烯（GO）和WS量子点，然后将WS量子点修饰在涂覆了RGO的棉织物上。表征研究证实剥落的WS二维薄片转变为WS零维量子点，以及氧化石墨烯（GO）转变为RGO。WS-QDs/RGO优化后的光电探测性能表明，在405nm照明源功率密度为1.4mW/mm²时，其光响应度为5.22mA/W。对于WS-QDs/RGO传感器，还发现了其他传感参数，如光敏度（约20.2%）、分辨率（约0.031mW/mm²/μA）、响应时间（(1.57s)）、恢复时间（(1.83s)）和比探测率（约(1.6×10^{11})琼斯），其中一些参数与已报道的一些器件相当，甚至更优。从WS量子点和RGO之间界面处适当的能带排列所引起的电荷转移角度对光传感机制进行了解释，其中纳米结构的维度和量子限制协同增强了异质结构的整体性能。通过弯曲、拉伸和扭转实验对器件的柔韧性进行了测试，并成功证明了其潜力。即使在浸泡在水中并随后干燥后，传感器性能仍显示出可重复使用的可能性。我们新型柔性光电探测器的柔韧性、高灵敏度和响应度、卓越的分辨率以及成本效益等特性，表明其在紫外波段工作的柔性和可穿戴光学探测器方面具有广阔的应用前景。尽管WS-QDs/RGO传感器的负光电导是导致其无法展现最佳性能的主要原因，但通过改进器件设计进行了权衡，以满足成为有竞争力器件的期望，并且这已通过实验事实得到了证明。
