  The EDGES collaboration has recently reported the detection of an
unexpectedly stronger absorption signal in the global 21-cm spectrum around
cosmic red-shift z = 17, resulting in the significant cooling of the primordial
gas. The cooling of the gas can be expected to occur by considering the
scattering off the baryons by a small fraction of DM carrying a tiny
electromagnetic charge (milli-charged DM). However, it turns out the energy
density of milli-charged DM obtained by considering thermal annihilation
through massless photons will get overproduced in the range of parameters
allowed by 21-cm line signal, if there are no new force carriers etc. In this
study, we argue that the milli-charged DM particles might get decoupled during
matter domination, in case there are moduli present in the theory. Therefore we
estimated the value of relic abundance of milli-charged DM by taking into
account an early matter dominated era. We found that for the value of modulus
mass around m_{\Phi} ~ 10^6TeV, the milli-charged DM particles could actually
yield the desired fraction of DM particles for the values of charge and DM
required to explain the 21-cm signal. Thus, the problem of an overproduction of
the milli-charged DM density in the desirable range of mass and charge of DM
can be evaded by considering an early moduli/matter dominated era.
