One-Step Synthesis of TiO2/Graphene Nanocomposites by Laser Pyrolysis with Well-Controlled Properties and Application in Perovskite Solar Cells

This work presents an original synthesis of TiO 2 /graphene nanocomposites using laser pyrolysis for the demonstration of efficient and improved perovskite solar cells. This is a one-step and continuous process known for nanoparticle production, and it enables here the elaboration of TiO 2 nanoparticles with controlled properties (stoichiometry, morphology, and crystallinity) directly grown on graphene materials. Using this process, a high quality of the TiO 2 /graphene interface is achieved, leading to an intimate electronic contact between the two materials. This effect is exploited for the photovoltaic application, where TiO 2 /graphene is used as an electron-extracting layer in n-i-p mesoscopic perovskite solar cells based on the reference CH 3 NH 3 PbI 3- x Cl x halide perovskite active layer. A significant and reproducible improvement of power conversion efficiencies under standard illumination is demonstrated, reaching 15.3% in average compared to 13.8% with a pure TiO 2 electrode, mainly due to a drastic improvement in fill factor. This beneficial effect of graphene incorporation is revealed through pronounced photoluminescence quenching in the presence of graphene, which indicates better electron injection from the perovskite active layer. Considering that a reduction of device hysteresis is also observed by graphene addition, the laser pyrolysis technique, which is compatible with large-scale industrial developments, is therefore a powerful tool for the production of efficient optoelectronic devices based on a broad range of carbon nano-objects.