Field assessment of Transparent Conductive Oxides Stability Under Outdoor Conditions

Large variety of optoelectronic and photosensitive devices are using essentially transparent conductive oxides (TCOs) as electrodes, such as panel displays, light emitting diodes, electrochromic devices and silicon heterojunction (SHJ) solar cells. The Sn doped $\text{In}_{2}\mathrm{O}_{3}$ (ITO) is the most commonly used transparent electrode-contact in SHJ technology. However, alternative TCO coatings have shown low parasitic absorption losses and higher electron mobility $(\mu_{\mathrm{n}})$ , and could be suitable alternatives enabling high sheet conductivities with low free-carrier absorption pending to show long term stability especially in outdoor real-world conditions. We report here on the electronic and optical properties of different TCOs, namely, ITO, IZO and IO:H deposited by DC or RF magnetron sputtering on glass substrates. TCOs were furthermore integrated into SHJ solar cell precursors and their carrier lifetimes were systematically investigated together with Hall-effect and spectroscopic analysis. The long-term stability of these different TCO coatings was evaluated at QEERI outdoor Test Facility site under real world outdoor conditions during 15 weeks characterized by heat and humidity, and their optoelectronic properties were systematically assessed.