Many varieties of layered inorganic-organic (IO) perovskite of type (R-NH3)2MX4 (where R: organic moiety, M: divalent metal, and X: halogen) were successfully fabricated and characterized. X-ray diffraction data suggest that these inorganic and organic structures are alternatively stacked up along c-axis, where inorganic mono layers are of extended corner-shared MX6 octahedra and organic spacers are the bi-layers of organic entities. These layered perovskites show unusual room-temperature exciton absorption and photoluminescence due to the quantum and dielectric confinement-induced enhancement in the exciton binding energies. A wide spectral range of optical exciton tunability (350 to 600 nm) was observed experimentally from systematic compositional variation in (i) divalent metal ions (M = Pb2+, Sn2+, Hg2+), (ii) halides (X = I- and Br-), and (iii) organic moieties (R). Specific photoluminescence features are due to the structure of the extended MX 2- 4 network and the eventual electronic band structure. The compositionally dependent photoluminescence of these IO hybrids could be useful in various photonic and optoelectronic devices. © Society of Photo-Optical Instrumentation Engineers.