We synthesized and characterized methylammonium (MA) mixed tri-halide tin perovskites (MASnIBr Cl ) for carbon-based mesoscopic solar cells free of lead and hole-transporting layers. Varied SnCl /SnBr ratios yielded tin perovskites with three halides (I, Br, and Cl) co-crystallized inside the tin-perovskite. When the SnCl proportion was ≥50 % (x≥1), phase separation occurred to give MASnI Br and MASnCl Br in the stoichiometric proportions of their precursors, confirmed by XRD. A device with MASnIBr Cl (SnCl =10 %) showed the best photovoltaic performance: J =14.0 mA cm , V =380 mV, FF=0.573, and PCE=3.1 %, and long-term stability. Electrochemical impedance spectra (EIS) show superior charge recombination and dielectric relaxation properties for the MASnIBr Cl cell. Transient PL decays showed the intrinsic problem of tin-based perovskites with average lifetimes less than 100 ps.