Tailoring the properties of Er-doped IZO thin films via controlled RF magnetron co-sputtering for photovoltaic applications

Abstract Er-doped indium zinc oxide (Er–IZO) thin films were deposited on glass substrates via radio-frequency magnetron co-sputtering, maintaining 90 W RF power on the IZO target while varying the Er DC power at 20, 30, and 40 W. XRD analysis showed that moderate Er incorporation (30 W) produced the largest crystallite size (31.76 nm), whereas excessive doping (40 W) reduced the coherence length to 28.40 nm due to increased lattice distortion. UV-VIS spectroscopy confirmed > 80% visible transparency for all samples, with the optical bandgap increasing from 3.28 eV (pristine) to 3.43 eV (20 W) and 3.80 eV (30 W) via the Burstein–Moss effect. A slight bandgap reduction to 3.50 eV at 40 W is attributed to defect-induced carrier compensation and enhanced scattering, which also caused minor transmission losses. Photoelectron spectroscopy revealed a non-monotonic work-function evolution: an initial decrease from 4.18 to 3.92 eV at 20 W, a modest increase to 3.94 eV at 30 W, and a larger rise to 4.32 eV at 40 W, driven by dopant clustering, carrier trapping, and electronic-structure modification. These results highlight the delicate balance between dopant incorporation, lattice integrity, and electronic behavior that governs the optimization of Er-doped IZO thin films as photovoltaic-relevant transparent conducting and optoelectronic materials.