The aluminum and titanium-doped zinc oxide films with improved blocking effect on copper diffusion

Abstract

Low-cost transparent conductive oxide films and copper metallization play a crucial role in the advancement of silicon heterojunction technologies (SHJ) to the terawatt level. However, the mechanisms of interfacial diffusion of copper through a zinc-based transparent conductive oxides (TCO) layer into silicon are still not known. In this study, we report that for the aluminum and titanium-doped zinc oxide (ATZO) films prepared by the magnetron sputtering method in the n-Si/110 nm TCOs/50 nm Cu structure, compared with indium tin oxide (ITO) and aluminum-doped zinc oxide (AZO), the blocking effect on copper diffusion can be comparable to that of ITO more than that of AZO. The results show that the measured band gap value of ATZO is 3.64 eV, and in terms of carrier concentration, ATZO has a value of 3.7 × 10²⁰ cm⁻³, which is much higher than the level of AZO. The sample with an ATZO layer also outperforms AZO in band gap, surface morphology, and conductivity, even after heat treatment up to 600 °C. It is important to note, however, that the high-temperature annealing used in this study may have induced changes in the crystallinity and alloy composition of the TCOs, which are not representative of typical SHJ operating conditions. Further studies with more moderate annealing temperatures are needed to better simulate real-world conditions. Nevertheless, ATZO films show strong potential as effective copper diffusion barriers in low-cost metallized photovoltaic applications, offering performance on par with ITO.