27.07.2021 Lead-free perovskite solar cells – How fluoride additives improve quality Tin halide perovskites are currently considered the best alternative to their lead-containing counterparts, which are, however, still significantly less efficient and stable. Now, a team led by Prof. Antonio Abate from HZB has analysed the chemical processes in the perovskite precursor solution and the fluoride compounds in detail. Using a clever combination of measurement methods at BESSY II and with NMR at the Humboldt-University Berlin, they were able to show that fluoride prevents the oxidation of tin and leads to a more homogeneous film formation with fewer defects, increasing the quality of the semiconductor layer.