Study of perovskite solar cells based mixed-organic-cation FAxMA1-xPbI3 absorption layer
The mixed-organic-cation FAxMA1-xPbI3 films were prepared using one-step solution deposition method in air ambient. The formamidinium (FA+) fraction ‘x’ was varied from 0.1 to 1 by changing the amount of formamidinium iodide (FAI) and Methylammonium iodide (MAI) in the precursor solution. The perovskite solar cells（PSCs）with the structure of FTO glass /compact TiO2 / mesoporous TiO2 / FAxMA1-xPbI3 /carbon electrode were designed and fabricated. The effects of FA+ fraction ‘x’ on structure, morphology and optical properties of FAxMA1-xPbI3 films, as well as photovoltaic performance of PSCs were studied. The results show that A photovoltaic inactive δ-phase FAPbI3 can be formed in the presence of a high content of FA+（x=0.8 and 1.0）. The band gap of FAxMA1-xPbI3 decrease from 1.58 eV to 1.49 eV when FA+ fraction x increase from 0.1 to1. The PSCs based on FA0.4MA0.6PbI3 exhibits an optimal photovoltaic performance, yielding Voc of 0.8 V, Jsc of 22.84 mA/cm2, FF of 0.48, and PCE of 8.77%.