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.