Band Alignment Boosts Charge-Carrier Collection in Sn-based Perovskite over Pb Counterparts

The
diverse elemental compositions endow metal halide perovskites
with tailorable electronic structures and broad optoelectronic applications.
For Sn-based perovskites, their bandedge positions, which govern interfacial
charge-carrier transport, are less well studied than their Pb counterparts.
In this work, the valence band maximum (VBM) of CsSnBr3 was experimentally and theoretically determined to be −5.2
eV, to which Au forms a good contact. The conduction band minimum
(CBM) of CsSnBr3 at −3.4 eV is matched by 1,3,5-tris­(4-phenylquinolin-2-yl)­benzene
(TQB), an organic electron transport material and a ligand to Sn­(II).
Thanks to proper band alignment, the device structure Al/TQB/CsSnBr3/Au constitutes a photodetector responsive to the entire visible
spectrum without a bias voltage and outperforms Pb-based devices under
similar conditions. Our results highlight the advantage of combined
experimental and theoretical tools in understanding intrinsic material
properties and guiding device fabrication.