Polymer Nanocomposites based on in situ reduced graphene oxide for photovoltaic applications in innovative hybrid solar cells

Polymeric nanocomposites based on UV in situ reduced graphene oxide were developed in order to enhance the electrical conductivity of polymeric matrices for the realization of highly efficient solid-state hybrid solar cells based on organometal trihalide perovskite absorbers. Graphene is a 2-D single layer of sp2-bonded carbon atoms characterized by high specific surface area, Young's modulus, thermal stability, mobility of charge carriers and plus fascinating transport phenomena such as the quantum Hall effect. Among several developed methods to prepare graphene, including chemical vapor deposition (CVD) and mechanical exfoliation, the chemical reduction of graphene oxide (GO) is regarded as the most promising for future implementation in large-scale production. In this work, a GO prepared by a modified Hummers method was used and reduced by a green method based on UV treatment in inert atmosphere. Graphene oxide reduction was monitored evaluating the change of absorption peak by UV-visible spectroscopy and X-ray photoelectron spectroscopy (XPS), monitoring the decrease of the oxygen groups linked to carbon. Dilute nanocomposites suspensions were then prepared by optimizing the dispersion procedure of GO in the polymeric matrix as function of process parameters, i.e. time, temperature and composition. Nanocomposite films were also realized by spin coating on different substrates and characterized by several techniques. At last the film showing the better properties was implemented in a hybrid solar cell to evaluate the increase of electrical conductivity and power conversion efficiency.