  The Ramaty High Energy Solar Spectroscopic Imager (RHESSI) X-ray data base
(February 2002 -- May 2006) has been searched to find solar flares with weak
thermal components and flat photon spectra. Using a regularised inversion
technique, we determine the mean electron flux distribution from count spectra
of a selection of events with flat photon spectra in the 15--20 keV energy
range. Such spectral behaviour is expected for photon spectra either affected
by photospheric albedo or produced by electron spectra with an absence of
electrons in a given energy range, e.g. a low-energy cutoff in the mean
electron spectra of non-themal particles. We have found 18 cases which exhibit
a statistically significant local minimum (a dip) in the range of 10--20 keV.
The positions and spectral indices of events with low-energy cutoff indicate
that such features are likely to be the result of photospheric albedo. It is
shown that if the isotropic albedo correction was applied, all low-energy
cutoffs in the mean electron spectrum were removed and hence the low energy
cutoffs in the mean electron spectrum of solar flares above $\sim$12 keV cannot
be viewed as real features in the electron spectrum. If low-energy cutoffs
exist in the mean electron spectra, the energy of low energy cutoffs should be
less than $\sim$12 keV.
