Optoelectronic Properties of (CH3NH3)3Sb2I9 Thin Films for Photovoltaic Applications

We present solution-based fabrication and characterization of the lead-free perovskite-related methylammonium antimony iodide (CH3NH3)(3)Sb2I9 compound. By photothermal deflection spectroscopy (PDS), we determined a peak absorption coefficient a approximate to 10(5) cm(-1) and an optical band gap of 2.14 eV for amorphous films of (CH3NH3)(3)Sb2I9. Compared to the related Bi compound, the Sb-perovskite shows no exciton peak in its absorption spectrum. The photoluminescence emission (PL) is observed at 1.58 eV, and the Urbach tail energy of this amorphous compound is E-u = 62 meV, indicating a substantial amount of energetic disorder. We fabricate a planar heterojunction solar cell with a (CH3NH3)(3)Sb2I9 absorber layer that yields a power conversion efficiency of eta approximate to 0.5%, already featuring a decent fill factor (FF) of 55% and open-circuit voltage of 890 mV but low photocurrent densities. The result of this basic study on (CH3NH3)Sb2I9 shows that this compound is a possible starting point for further research into Sb-based lead-free perovskite solar cells.