Environmental stability of high-mobility indium-oxide based transparent electrodes

Large-scale deployment of a wide range of optoelectronic devices, including solar cells, critically depends on the long-term stability of their front electrodes. Here, we investigate the performance of Sn-doped In₂O₃ (ITO), H-doped In₂O₃ (IO:H), and Zn-doped In₂O₃ (IZO) electrodes under damp heat (DH) conditions (85 °C, 85% relative humidity). ITO, IO:H capped with ITO, and IZO show high stability with only 3%, 9%, and 13% sheet resistance (R_s) degradation after 1000 h of DH, respectively. For uncapped IO:H, we find a 75% R_s degradation, due to losses in electron Hall mobility (μ_Hall). We propose that this degradation results from chemisorbed OH- or H₂O-related species in the film, which is confirmed by thermal desorption spectroscopy and x-ray photoelectron spectroscopy. While μ_Hall strongly degrades during DH, the optical mobility (μ_optical) remains unchanged, indicating that the degradation mainly occurs at grain boundaries