  We report emergence of photoluminescence at room temperature in trigonal
$Cs_3Bi_2Br_9$ at high pressures. Enhancement in intensity with pressure is
found to be driven by increase in distortion of $BiBr_6$ octahedra and
iso-structural transitions. Electronic band structure calculations show the
sample in the high pressure phase to be an indirect band gap semiconductor. The
luminescence peak profile show signatures related to the recombination of free
and self trapped excitons, respectively. Blue shift of the both peaks till
about 4.4 GPa are due to the exciton recombination before relaxation due to the
decrease in exciton lifetime with scattering from phonons
