Tunable Doping and Characterization of Single-Wall Carbon Nanotube Macrosystems for Electrode Material Applications

We present an efficient method for easy tuning of optical and electrophysical parameters of macroscopic objects formed from single-wall carbon nanotubes (SWCNTs). We have developed a unique step-by-step doping procedure by filling the SWCNT inner channels with acceptors and donors in gaseous conditions. The main parameter that tailors the film properties is the dopant concentration in the SWCNT channels varied through the gaseous filling time. The ambient oxygen impact on the doping level has been measured and analyzed for all considered SWCNT objects. Our approach provides a predictable shift of Fermi level position in the range of 0.1-0.9 eV and the optical band gap edge value between 0.4 and 1.1 eV. The tuning method was applied to optimize the thermopower performance of SWCNT films. We have measured the maximum possible values of the power factor and thermoelectric coefficient and studied the stability of these parameters in the air for studied samples. On the basis of the revealed relation between thermopower and sheet resistance, we propose a general approach for characterization of conducting CNT macro-objects, which we call the "doping map"plotting. This empirical method allows to predict stable, maximum, or optimal values for the transport, thermopower, and optical characteristics of materials in the air. Our findings are prospective for prediction and tailoring of SWNT-containing materials properties used in such technological applications, as electrochemical, sensor, solar cell, or thermoelectric electrode materials.