Strong room-temperature ultraviolet to red excitons from inorganic organic-layered perovskites, (R-NH3)2MX4 (M=Pb2+, Sn2+, Hg2+; X=I−, Br−)

Abstract

Many varieties of layered inorganic-organic (IO) perovskite of type (R-NH 3 ) 2 MX 4 (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 MX 6 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=Pb 2+ , Sn 2+ , Hg 2+ ), (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.