Dopant-Tunable Ultrathin Transparent Conductive Oxides for Efficient Energy Conversion Devices
Dae Yun Kang, Bo‐Hyun Kim, Tae Ho Lee, Jae Won Shim, Sungmin Kim, Ha‐Jun Sung, K. J. Chang, Tae Geun Kim
Abstract
Abstract 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.