This paper reports the extensive investigation of the luminescence properties of the bismuth triiodide, BiI3, layered semiconductor. The luminescence spectrum is comprised of relatively narrow stacking fault excitons (R, S, and T) in addition to broader bands at lower energies. The present work emphasizes the investigation of the broader bands. Research of the BiI3 involved utilization of continuous-wave photoluminescence (PL) and PL excitation (PLE), together with two modulated techniques : thermal-modulated PL (TMPL) and microwave-modulated PL (MMPL). The TMPL and the MMPL of the stacking fault excitons served to confirm the previously suggested interaction among the R, S, and T states. Experimental evidence indicates that the broader emission lines may be divided into several subgroups, some of which are associated with band edge to deep state transitions. The deep state within the band gap may be attributed to stoichiometric or strain defects. Results showed that the latter transitions correlated to band edge properties. One Subgroup, however, displayed independent behavior, due mainly to an absence of coupling to the band edge. This subgroup is associated with a transition between relatively localized donor and acceptor states.