Deep-blue light emitting diode based on defect variations of a 2D hybrid organic-inorganic low dimensional perovskite semiconductor

Abstract: 2D hybrid organic-inorganic semiconductors (HOIS) are low-cost, self-assembled semiconductors that have proven to be vital for novel optoelectronic devices due to their inherent stable excitons even at room temperature. 2D HOIS are chemically stable with respect to the 3D analogues, but their inherent anisotropy complicates their implementation in devices, including electroluminescence (EL) devices. We report on the synthesis, characterization, cathodoluminescence and EL of a new 2D HOIS, (4-fluoro phenethylamine-H)2PbBr4, and its defect variations (DVs). The latter, in contrast to the pristine material, allow for the first time the simple fabrication of a prototype blue EL device by coating DVs on a conducting anode substrate and using a Ga/In droplet cathode. DVs' optimization can lead to improved light emitting devices (LEDs) and the work here is expected to provide the incentive for utilizing HOIS DVs, as these are compatible with industrial scale synthesis. In contrast to the pristine iodine analogue, whose thin films readily provide EL, only the DVs or mixtures with MoS2 nano-sized platelets provide EL, after careful deposition. These exhibit defects that disrupt the planar non-conductive nature of the micrometric 2D HOIS platelets, usually aligned parallel to the substrate, thus, providing mechanisms for current flow. Finally, the choice of the fluorine-modified amine enhances the functionality of the DVs as LED materials compared to using unmodified amine due to the repulsion among the amine tails, leading to stable decorated 2D inorganic sheets that are weakly bound.