  Hot carrier solar cells hold promise for exceeding the Shockley-Queisser
limit. Slow hot carrier cooling is one of the most intriguing properties of
lead halide perovskites and distinguishes this class of materials from
competing materials used in solar cells. Here we use the element selectivity of
high-resolution X-ray spectroscopy to uncover a previously hidden feature in
the conduction band states, the {\sigma}-{\pi} energy separation, and find that
it is strongly influenced by the strength of electronic coupling between the
A-cation and bromide-lead sublattice. Our finding provides an alternative
mechanism to the commonly discussed polaronic screening and hot phonon
bottleneck carrier cooling mechanisms. Our work emphasizes the optoelectronic
role of the A-cation, provides a comprehensive view of A-cation effects in the
electronic and crystal structures, and outlines a broadly applicable
spectroscopic approach for assessing the impact of chemical alterations of the
A-cation on halide and potentially non-halide perovskite electronic structure.
