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

Abstract

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 x 10(22) to 4.99 x 10(21) cm(-3) with increasing the IGZO thickness, while the charge mobility insignificantly changed from 19.07 to 19.62 cm(2)/V. The samples had sheet resistances of 4.17-4.39 Omega/sq with increasing IGZO thickness, while the resistivity increased from 1.89 x 10(-5) to 6.43 x 10(-5) Omega 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 x 10(-3) Omega(-1). (C) 2015 Elsevier B.V. All rights reserved.