In this paper, we have investigated the possibility to realize a nanocomposite buffer layer for perovskite solar cells, based on polyelectrolyte poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) PEDOT:PSS and graphene oxide (GO). To this aim, GO, prepared by a modified Hummers method, was mixed with PEDOT:PSS by solvent swelling method and reduced in situ into the polymer matrix through a green and simple method, by using UV radiation. Thin nanocomposite layers were spin coated on different substrates and characterized by several techniques. GO reduction was first analyzed by XPS analyses, monitoring the decrease of the intensity of the peak of the oxygen groups linked to carbon. The grade of the dispersion of GO into PEDOT:PSS was also analyzed by scanning electron microscopy. Sheet resistance measurements of the films with and without GO before and after UV treatment was …