We
report valence and conduction band densities of states measured
via ultraviolet and inverse photoemission spectroscopies on three
metal halide perovskites, specifically methylammonium lead iodide
and bromide and cesium lead bromide (MAPbI3, MAPbBr3, CsPbBr3), grown at two different institutions
on different substrates. These are compared with theoretical densities
of states (DOS) calculated via density functional theory. The qualitative
agreement achieved between experiment and theory leads to the identification
of valence and conduction band spectral features, and allows a precise
determination of the position of the band edges, ionization energy
and electron affinity of the materials. The comparison reveals an
unusually low DOS at the valence band maximum (VBM) of these compounds,
which confirms and generalizes previous predictions of strong band
dispersion and low DOS at the MAPbI3 VBM. This low DOS
calls for special attention when using electron spectroscopy to determine
the frontier electronic states of lead halide perovskites.
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