Improvement of field emission performances by DMSO and PEDOT:PSS treated freestanding CNT clusters

In this paper, we present two methods to improve the field emission (FE) performance of vertically aligned carbon nanotube emitters that are treated with dimethyl sulfoxide (DMSO) solution and poly(3,4-ethylene dioxythiophene):polystyrene sulfonate (PEDOT:PSS) solution, respectively, and compared their performances. Both treatments force CNTs to be bundled into clusters, but the formed structures are very different. After treatment, both methods reduced the threshold electric field due to the reduction in screening effects, whereas the PEDOT:PSS treatment significantly reduced the threshold field to far lower than that of DMSO treatment. In addition, the FE efficiency and lifetime of treated CNT emitters are significantly improved. For both treated emitters, there is only slight degradation of the emission current after 80 hours of continuous FE at around 50 μA. In addition, the uniformity of both treated CNT emitters is improved which enables more CNTs to contribute to the overall current emission. This, in turn, lowers the current emitted by individual CNTs, and thereby increases the lifetime of the emitters. Therefore, this study demonstrates that these simple treatment methods of bundling CNTs into unique cluster-structures significantly improve the lifetime of FE and make them excellent candidates for large currents and long-term FE.