Controlled Lattice Thermal Conductivity of Transparent Conductive Oxide Thin Film via Localized Vibration of Doping Atoms

Abstract

Amorphization using impurity doping is a promising approach to improve the thermoelectric properties of tin-doped indium oxide (ITO) thin films. However, an abnormal phenomenon has been observed where an excessive concentration of doped atoms increases the lattice thermal conductivity (κl). To elucidate this paradox, we propose two hypotheses: (1) metal hydroxide formation due to the low bond enthalpy energy of O and metal atoms and (2) localized vibration due to excessive impurity doping. To verify these hypotheses, we doped ZnO and CeO2, which have low and high bond enthalpies with oxygen, respectively, into the ITO thin film. Regardless of the bond enthalpy energy, the κl values of the two thin films increased due to excessive doping. Fourier transform infrared spectroscopy was conducted to determine the metal hydroxide formation. There was no significant difference in wave absorbance originating from the OH stretching vibration. Therefore, the increase in κl due to the excessive doping was due to the formation of localized regions in the thin film. These results could be valuable for various applications using other transparent conductive oxides and guide the control of the properties of thin films.

Solution-Processed SnO2 Quantum Dots for the Electron Transport Layer of Flexible and Printed Perovskite Solar Cells

“…The TCO layer is typically made of indium-doped tin oxide (ITO). However, other alternatives also exist [ 21 , 22 , 23 ].…”

Precision Doping of Iodine for Highly Conductive Copper(I) Iodide Suitable for the Spray-Printable Thermoelectric Power Generators

“…Advantageous transparent conductive (TC) TE materials possessing a large Seebeck coefficient and low thermal conductivity have been widely investigated because of their applicability to next-generation technologies such as smart windows and screens for generating electricity from solar radiation or halogen lamp heat sources in an indoor environment. Unfortunately, most TC TE materials (zinc oxide, indium oxide, indium tin oxide, and strontium titanium oxide) exhibit n -type TE properties. − Consequently, it is essential to develop air-stable and highly conductive p -type TC TE materials, as n -type counterparts, for realizing efficiently integrated thermoelectric generators (TEGs) with high power outputs. Recently, copper iodide (CuI) has been touted as a promising p -type TC TE material because it demonstrates several advantages, such as facile control of its electronic and phonon transport properties, and CuI is easily accessible through many synthetic methods. − The high intrinsic electrical conductivity of CuI results from copper vacancies with high hole mobility and this can be further improved by controlling the iodine content through engineered doping. − Furthermore, as a heavy element, iodine is favorable for TE performance improvements because it can reduce the lattice thermal conductivity.…”