posted on 2016-06-21, 00:00authored byJan-Christoph Hebig, Irina Kühn, Jan Flohre, Thomas Kirchartz
We present solution-based fabrication
and characterization of the
lead-free perovskite-related methylammonium antimony iodide (CH3NH3)3Sb2I9 compound.
By photothermal deflection spectroscopy (PDS), we determined a peak
absorption coefficient α ≈ 105 cm–1 and an optical band gap of 2.14 eV for amorphous films of (CH3NH3)3Sb2I9. 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 Eu = 62 meV, indicating a
substantial amount of energetic disorder. We fabricate a planar heterojunction
solar cell with a (CH3NH3)3Sb2I9 absorber layer that yields a power conversion
efficiency of η ≈ 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)3Sb2I9 shows that this compound
is a possible starting point for further research into Sb-based lead-free
perovskite solar cells.