  Hot carrier solar cells promise theoretical power conversion efficiencies far
beyond the single junction limit. However, practical implementations of hot
carrier solar cells have lagged far behind those theoretical predictions.
Reciprocity relations for electro-luminescence from conventional single
junction solar cells have been extremely successful in driving their efficiency
ever closer to the theoretical limits. In this work, we discuss how the
signatures of a functioning hot carrier device should manifest experimentally
in electro-luminescence and dark $I-V$ characteristics. Hot carrier properties
lead to deviations from the Shockley diode equation that is typical for
conventional single junction solar cells. These deviations are directly linked
to an increase in temperature of the carriers and therefore the temperature
measured from electro-luminescence spectra. We also elucidate how the behaviour
of hot carrier solar cells in the dark depends on whether Auger processes play
a significant role, revealing a stark contrast between the regime of negligible
Auger recombination (carrier conservation model) and dominant Auger
recombination (Impact Ionization model) for hot carrier solar cells.
