Fabrication of a carbon nanotube/tungsten disulfide visible spectrum photodetector.

Two-dimensional-material-based photodetectors are gaining prominence in optoelectronic applications, but there are certain factors to consider with bulk material usage. The demand for a highly responsive and highly efficient device with an inexpensive fabrication method is always of paramount importance. Carbon nanotubes (CNT) are well known, owing to their upheld vigorous structural and optoelectronic characteristics, but to fabricate them at a large scale involves multifarious processes. A visible range photodetector device structure developed using a simple and inexpensive drop-casting technique is reported here. The optoelectronic characteristics of the device are studied with IV measurements under the light and dark conditions by incorporating a thin CNT layer on top of tungsten-disulfide-based heterojunction photodetector to enhance the overall characteristics such as detectivity, responsivity, photocurrent, rise time, and fall time in the visible range of the light spectrum with a violet light source at 441 nm. In the DC bias voltage range of −20 to 20 V, IV measurements are carried out under dark and illumination conditions with different incident power densities. The threshold voltage is recognized at 2.0 V. Photocurrent is found to be highly dependent on the state of the incident light. For 0.3074mW/cm2 illuminated power, the highest responsivity and detectivity are determined to be 0.57 A/W and 2.89×1011 Jones. These findings encourage an alternative fabrication method at a large scale to grow CNTs for the enhancement of optoelectronic properties of present two-dimensional-material-based optoelectronic and photonics applications.