The role of graphene-doped PEDOT:PSS as hole transporting layer in inverted perovskite solar cells

The undesirable reactions from poly(3,4-ethylenedioxythiophene):poly (styrene sulfonate) (PEDOT:PSS), which presents hygroscopic and acid character of PSS- group, reduces drastically the stability and efficiency of inverted perovskite solar cells. We developed a facile synthesis method of graphene platelets into PEDOT:PSS solution in order to block these unstable reactions. The homogenous graphene-doped PEDOT:PSS layer show up to 10 times improvements on its conductivity, maintaining high optical transmittance. Additionally, the standard CH3NH3PbI3 film grown on graphene-doped PEDOT:PSS layer exhibits large perovskite crystallite size and a reduction of PbI2 content, leading high stability over time. The hydrophobic character of graphene probably blocks undesirable reactions hampering degradation. The inverted perovskite solar cells based on graphene-doped PEDOT:PSS as hole transport layer show better photovoltaic parameters by increasing charge extraction analyzed by impedance spectroscopy. This simple and low-cost preparation method leads to a successful candidate to synthetize effective hole transport layer to be considered in optoelectronic devices.