Ti0$_2$/graphene-based nanocomposite as electron transport layer for perovskite solar cells: synthesis and properties

International audienceSince 2012, hybrid solar cells based on perovskite materials demonstrated several significant advances, with power conversion efficiencies now over 22%, attracting strong interest within the scientific community. Still, efforts remain to be performed to improve photo-current extraction, especially concerning the development of efficient and reliable charge transporting electrodes and selective contacts. "Titanium dioxide mesoporous layer, while remaining an important component for perovskite structuration and electron transport in high efficiency devices, can however still promote charge trapping and recombination. To reduce these phenomena and improve electron collection, our strategy consists in using the excellent conductivity properties of graphene materials through its incorporation within the Ti0$_2$ electrode. In this context, we develop high quality Ti0$_2$/graphene composites in a single step by using the singular technique of laser pyrolysis that enables to synthesize nanoparticles with well-controlled properties, tuned for an optimal energy conversion. We combine here this specific know-how on material synthe sis with our know-how on perovskite solar cells processing. We pay particular attention to material characterizations su ch as morphological and structural analysis as weIl as physical properties evaluation of the nanocomposites and their role and effects within solar cells. Our first results show a larger conductivity of the Ti0$_2$ layer in presence of graphene, as well as larger photocurrents and sm aller series resistance under standard illuminatioij, traducing the benefits of graphene for a better charge collection in the device. More generally, a significant increase in power conversion effiëiency is observed for perovskite solar cells containing graphene in the Ti0$_2$ mesoporous layer, demonstrating the benefit of the laser pyrolysis process for the production ofhigh quality electron transport layer