Simultaneously Improving Solution Processing and Electronic Doping in Carbon Nanotube Thermoelectrics

Abstract

Thermoelectrics are solid state devices that convert waste heat into electricity. Their abundancy and low toxicity makes carbon materials good candidates for thermoelectric applications requiring large areas and operation at low to medium temperatures [1]. Carbon nanotubes (CNTs) offer generally good electrical conductivity, which is a must for thermoelectrics. While their Seebeck coefficient can also be high, it has been shown to decrease as the conductivity increases. Optimum performance, therefore, requires a fine tuned doping level in order to find the sweet spot. On the other side, CNTs are often difficult to process, which may limit its applicability for this type of applications.In this invited talk, I will present two different strategies that our group is using in order to simultaneously improve processing capabilities and control doping level. First we will discuss the use of composites of CNTs and highly soluble polymers. Electron withdrawing or donating polymers, such as PEI and P3HT, respectively, help disperse the CNTs and simultaneously dope the CNT p- or n-type [2,3]. Alternatively, the use of bacteria to produce composites of cellulose and CNTs provides additional means of producing high performing composites [4]. Finally, I will describe our latest work on the use of alkali metals to form real CNT solutions and simultaneously produce stable n-doping of the resulting buckypapers [5].[1] Will organic thermoelectrics get hot? M. Campoy-Quiles, Philosophical Transactions of the Royal Society A, 377, 20180352 (2019).[2] Photoinduced p- to n-type Switching in Thermoelectric Polymer-Carbon Nanotube Composites, B. Dörling, J. D. Ryan, J. D. Craddock, A. Sorrentino, A. El Basaty, A. Gomez, M. Garriga, E. Pereiro, J. E. Anthony, M. C. Weisenberger, A. R. Goñi, C. Müller and M. Campoy-Quiles, Advanced Materials, 28, 2782 (2016).[3] Investigating thermoelectric stability under encapsulation using PEI‐Doped CNT films as a model system, F. Abdallah, L. Ciammaruchi, A. Jiménez‐Arguijo, E.S.M. Duraia, H.S. Ragab, B. Dörling and M. Campoy‐Quiles, Advanced Materials Technologies, 5, 2000256 (2020).[4] Farming thermoelectric paper, D. Abol-Fotouh, B. Dörling, O. Zapata-Arteaga, X. Rodríguez-Martínez, A. Gómez, J. S. Reparaz, A. Laromaine, A. Roig and M. Campoy-Quiles, Energy and Enviromental Science, 12, 716-726 (2019).[5] Soluble Alkali-Metal CNT Salts for n-type Thermoelectric Composites, B. Dörling, X. Rodríguez-Martínez, I. Álvarez-Corzo, M. Campoy-Quiles, submitted (2021).