Dopant-Tunable Ultrathin Transparent Conductive Oxides for Efficient Energy Conversion Devices

Abstract

Highlights

• Dopant-tunable transparent conductive oxide (≤ 50 nm) fabricated via electric-field-driven metal implantation (m-TCOs; m= Ni, Ag, and Cu) is demonstrated.

• The m-TCOs exhibit ultrahigh transparency, low sheet resistance, and broad work function tunability, leading to outstanding performance in various optoelectronic devices.

• The work function change is attributed to the interstitial metal atoms that provide the empty d-orbital, resulting in the shift of the Fermi level.

Ultrathin film-based transparent conductive oxides (TCOs) with a broad work function (WF) tunability are highly demanded for efficient energy conversion devices. However, reducing the film thickness below 50 nm is limited due to rapidly increasing resistance; furthermore, introducing dopants into TCOs such as indium tin oxide (ITO) to reduce the resistance decreases the transparency due to a trade-off between the two quantities. Herein, we demonstrate dopant-tunable ultrathin (≤ 50 nm) TCOs fabricated via electric field-driven metal implantation (m-TCOs; m = Ni, Ag, and Cu) without compromising their innate electrical and optical properties. The m-TCOs exhibit a broad WF variation (0.97 eV), high transmittance in the UV to visible range (89–93% at 365 nm), and low sheet resistance (30–60 Ω cm⁻²). Experimental and theoretical analyses show that interstitial metal atoms mainly affect the change in the WF without substantial losses in optical transparency. The m-ITOs are employed as anode or cathode electrodes for organic light-emitting diodes (LEDs), inorganic UV LEDs, and organic photovoltaics for their universal use, leading to outstanding performances, even without hole injection layer for OLED through the WF-tailored Ni-ITO. These results verify the proposed m-TCOs enable effective carrier transport and light extraction beyond the limits of traditional TCOs.