  Organic-inorganic halide perovskites have been intensively re-investigated
due to their applications, yet the opto-electronic function of the organic
cation remains unclear. Through organic-selective resonant Auger electron
spectroscopy measurements on well-defined single crystal surfaces, we find
evidence for electronic coupling in the unoccupied states between the organic
and inorganic sub-lattices of the prototypical hybrid perovskite, which is
contrary to the notion based on previous studies that the organic cation is
electronically inert. The coupling is relevant for electron dynamics in the
material and for understanding opto-electronic functionality.
