In recent years, metal-halide perovskites have attracted much attention as promising materials for optoelectronic devices such as light-emitting diodes, photovoltaic cells and lasers. Especially, Pb-based perovskites have demonstrated outstanding achievements as emitters in perovskite light-emitting diodes (PeLEDs). However, the toxicity of Pb and the inherent instability of these Pb-based perovskites are the main obstacles against large-scale and commercial application. Sn-based perovskites are currently emerging as an alternative to the Pb-based perovskites but researchers have difficulty developing efficient Sn-based PeLEDs because they have metallic behavior arising from the self-oxidation from Sn2+ to Sn4+ and produce poor film morphology with incomplete surface coverage. Here, we employed Pb-free perovskite, CsSnBr3, as an emitter of PeLEDs to avoid the toxicity issue and proposed two strategies to overcome the limitations of the Sn-based perovskites. First, we introduced Cs instead of the widely-used organic cations such as methylammonium (MA) or formamidinium (FA) because it acts as a strong oxygen binder which can suppress the oxidation of Sn2+ to Sn4+. Furthermore, the additional introduction of SnF2 to the perovskite precursor reduced the Sn vacancies, and correspondingly the metallic conductivity. We also improved the perovskite film morphology (i.e., surface coverage) by optimizing the SnF2 content in the perovskite precursor. We analyzed the crystal structures of CsSnBr3 using x-ray diffraction (XRD) and observed a sharp and narrow photoluminescence (PL) spectrum. Finally, we demonstrated bright Pb-free PeLEDs based on CsSnBr3.