One-step, solution-processed formamidinium lead trihalide (FAPbI(3-x)Cl(x)) for mesoscopic perovskite-polymer solar cells.

Formamidinium (FA) lead triiodide perovskite with chlorine addition (NH2CH=NH2PbI(3-x)Clx) is employed as a light harvester in mesoscopic solar cells for the first time. It is demonstrated that a phase-pure FAPbI(3-x)Clx perovskite layer can be synthesized using a one-step solution-process at 140 °C, and the resultant solar cells deliver a maximum power conversion efficiency of 7.51%, which is the most efficient formamidinium-lead-halide perovskite mesoscopic solar cell employing a polymer hole-transporting layer. The effects of the thermal annealing temperature on the quality/morphology of the perovskite layer and the solar cells performance are discussed. The advantages offered by the one-step solution-processing method and the reduced bandgap make FAPbI(3-x)Clx perovskites an attractive choice for future hybrid photovoltaics.