Optimization of transmittance and resistance of indium gallium zinc oxide/Ag/indium gallium zinc oxide multilayer electrodes for photovoltaic devices

• The opto-electrical properties of IGZO/Ag/IGZO multilayer films are investigated.
• Transmission window widens and shifts to lower energies with increasing IGZO thickness.
• IGZO(39 nm)/Ag(19 nm)/IGZO(39 nm) shows maximum transmittance at 520 nm.
• Carrier concentration decreases, but sheet resistance is constant with IGZO thickness.

We report on the optimization of the optical and electrical properties of IGZO/Ag/IGZO multilayer films as a function of IGZO thickness. The transmission window slightly widened and shifted toward lower energies with increasing IGZO thickness. The IGZO(39 nm)/Ag(19 nm)/IGZO(39 nm) showed transmittance 88.7% at 520 nm. The optical transmittance spectra were examined by finite-difference time-domain (FDTD) simulations. The carrier concentration decreased from 1.73 × 1022 to 4.99 × 1021 cm−3 with increasing the IGZO thickness, while the charge mobility insignificantly changed from 19.07 to 19.62 cm2/V. The samples had sheet resistances of 4.17–4.39 Ω/sq with increasing IGZO thickness, while the resistivity increased from 1.89 × 10−5 to 6.43 × 10−5 Ω cm. The 39 nm-thick IGZO multilayer sample had a smooth surface with a root mean square roughness of 0.63 nm. The IGZO(39 nm)/Ag(19 nm)/IGZO(39 nm) multilayer showed a Haacke's FOM of 49.94 × 10−3 Ω−1.