It is a new type of functional material that can greatly adjust the photoelectric, electrocatalytic, and thermoelectric properties of indium oxide through the addition of copper, making it suitable for a variety of high-tech applications.

1. Characteristics

1) Adjustment of electrical performance

    ・The carrier concentration and resistivity of indium oxide can be significantly changed through the addition of copper.

       For example, the resistivity of a 4.09 at% Cu-doped In₂O₃ film can reach 30.2 × 10-³ Ω-cm, increasing the carrier concentration         to 3.72 × 10²⁰ cm-³ but decreasing the mobility to 0.56 cm²V-¹s-¹.

   ・In electrocatalytic applications, the synergistic effect of copper and indium oxide optimizes the electron transport pathway and    increases catalytic activity.

2) Change in optical performance

   ・The addition of copper decreases the optical band gap of indium oxide (from 3.76 eV to 2.71 eV) and significantly reduces the    visible light transmission of the film, making it suitable for infrared and wavelength-specific optoelectronic devices.

3) Improved catalytic performance

   ・In the electrolytic CO₂ reduction reaction (CO₂RR), Cu-In₂O₃ composite suppresses the carbon-carbon coupling reaction,   

      promotes the desorption of CO₂ intermediates, and improves CO selectivity (Faraday efficiency up to 80-95%).

   ・The addition of copper also increases the hydrophobicity of the material, which increases the CO₂ concentration at the solid- 

      liquid interface and further improves the catalytic efficiency.

4) Optimization of thermoelectric properties

  ・In In₂O₃/Pt thermocouples, the thermoelectric potential (152.1-70.5 μV/°C) is modulated by the addition of copper and can be    used for high temperature sensing applications.

5) Structural Stability

   ・Copper addition improves the crystallinity of indium oxide thin films, which increases stability at high temperatures and in     

      corrosive environments.

2. Main Applications

1) Electrocatalytic CO₂ reduction

   ・For highly efficient CO₂-to-CO conversion with Faraday efficiencies of up to 80% in H-type electrolysis cells and up to 95% in     

      MEA reactors. 

2) Transparent Conductive Oxide (TCO)

   ・Used for flexible electronics, solar cell electrodes, etc.

  Copper addition reduces transmittance, but conductivity can be optimized for specific optoelectronic applications.

3) Thermoelectric sensors

   ・Used for temperature monitoring in high temperature environments (industrial furnaces, aerospace, etc.), copper addition   

      optimizes the output performance of In₂O₃/Pt thermocouples.

4) Photoelectrochemical devices

   ・As an alternative material for water oxidation catalysts with cost advantages over conventional ITO for photoelectrochemical     

      electrolytic cells.

5) Hole transport layer for solar cells

    ・Copper-doped indium oxide thin film can be used as a hole transport layer in calcium titanium ore solar cells to increase device    efficiency.