Scalable and Surfactant-Free Process for Single-Walled Carbon Nanotube Based Transparent Conductive Thin Films via Layer-by-Layer Assembly

In this paper, we demonstrate a surfactant-free method to fabricate large-area SWCNT film based transparent conductive (SWCNT-TC) electrodes with uniform properties (optical and electrical) via the fusion of layer-by-layer (LBL) deposition. The optical and electrical properties of SWCNT-TC electrodes are comparable to those of typical metal oxide electrodes after the SWCNT-TC electrode is further treated by acid (HNO₃/H₂SO₄) and SOCl₂. The sheet resistance of SWCNT-TC electrodes is measured to be ∼34.9 Ω/sq and the transmittance is ∼71.9% at 550 nm. Moreover, our work addressed a long-term argument regarding whether the improvement in conductivity of SWCNT-TC electrodes after acid treatment is, as was proposed, attributed to sufficient removal of surfactant; our result implicitly indicates that the improved conductivity may be due to the down-shifting of the Fermi level induced by the charge transfer between the SWCNTs and doped species after acid treatment. In addition, the high quality (I(D)/I(G) < 1) and surfactant-free SWCNT-TC electrode shows higher performance in an organic photovoltaic (OPV) device as compared with those of surfactant-contained SWCNT-TC electrodes made by other processes.