Simultaneous mid-infrared transmission and electromagnetic shielding with high-mobility cerium-doped In₂O₃ thin films

Conventional metal mesh structures, used for infrared (IR) transparent electromagnetic interference (EMI) shielding, often compromise optical imaging quality and suffer from mechanical instability. While continuous transparent conductive films offer superior imaging and adhesion, they typically exhibit an inherent trade-off between mid-infrared (MIR) transmittance and shielding effectiveness (SE). To overcome these limitations, we propose high-valence cerium doping of indium oxide (In₂O₃) via the principle of similar effective ionic radius to optimize carrier transport. This work thoroughly investigates the largely unexplored potential of cerium-doped In₂O₃ (ICO) thin films for MIR optoelectronic applications. We analyze the interplay between film composition, structure, and the resulting conductive mechanism to achieve exceptional performance. The optimized ICO film achieves a high Hall mobility of 103 cm²/V·s, an MIR transmittance exceeding 73% at 4 µm, and an EMI SE above 13 dB across the 5.4–18 GHz frequency band. These properties are attributed to the high mobility and plasma frequency tuning enabled by Ce doping. Our findings reveal the significant potential of ICO thin films for advanced optoelectronic and EMI shielding devices, particularly in harsh environments. This study provides crucial insights into the development of high-performance, continuous transparent electrodes that simultaneously achieve excellent MIR transparency and effective EMI shielding.