Temperature-dependent time-resolved photoluminescence of (C6H5C2H4NH3)2PbX4 (XÂ =Â Br and I)

► Exciton dynamics are investigated by temperature-dependent time-resolved photoluminescence. ► (C6H5C2H2NH3)2PbI4 showed only singlet excitons. ► In contrast, (C6H5C2H4NH3)2PbBr4 showed triplet excitons at low temperatures. ► The local structure between the organic and inorganic layers plays a prominent role in the formation of triplet excitons.