A numerical process is developed on a Transfer-Matrix Method (TMM) to calculate the optical properties of multilayers involved in thin film solar cells. Using the bulk complex refractive indices in a considered spectral range for each material allows us to calculate the transmittance of the whole structure and the intrinsic absorption inside the sole active layer. An optical optimization of oxidelmetalloxide trilayer electrode in the air and with a (poly-3-hexylthiophene):[6,6]-phenyl-C-61-butyric acid methyl ester (P3HT:PCBM) bulk heterojunction based organic solar cell is performed. The ZnOlAgIZnO structure is specifically studied in order to avoid the use of indium in such photovoltaic components. (C) 2014 Elsevier B.V. All rights reserved.