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Abstract This work reports important fundamental advancements in multiwall carbon nanotube (MWCNT) rectenna devices by creating and optimizing new diode structures to allow optical rectification with air‐stable devices. The incorporation of double‐insulator layer tunnel diodes, fabricated for the first time on MWCNT arrays, enables the use of air‐stable top metals (Al and Ag) with excellent asymmetry for rectification applications. Asymmetry is increased by as much as 10 times, demonstrating the effectiveness of incorporating multiple dielectric layers to control electron tunneling in MWCNT diode structures. MWCNT tip opening also reduces device resistance up to 75% due to an increase in diode contact area to MWCNT inner walls. This effect is consistent for different oxide materials and thicknesses. A number of insulator layers, including Al₂O₃, HfO₂, TiO₂, ZnO, and ZrO₂, in both single‐ and then double‐insulator configurations are tested. Resistance increases exponentially with insulator thickness and decreases with electron affinity. These results are used to characterize double‐insulator diode performance. Finally, for the most asymmetric device structure, Al₂O₃‐HfO₂(4/4 nm), optical rectification at a frequency of 470 THz (638 nm) is demonstrated. These results open the door for designing efficient MWCNT rectenna devices with more material flexibility, including air‐stable, transparent, and conductive top electrode materials.