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Defect Variants Based on the 2D Hybrid Organic–Inorganic Low-Dimensional Semiconductor (4-Fluoro-phenethylamine‑H)2PbBr4 for Fabrication of Single-Layer Deep Blue LEDs

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posted on 25.04.2018, 00:00 by Ioanna Vareli, Anastasia Vassilakopoulou, Ioannis Koutselas
The low-cost and self-assembled hybrid organic–inorganic semiconductors (HOIS) appear lately to be ideal for novel optoelectronic devices due to their inherent stable excitonic states, even at room temperature. 2D HOIS, superlattices of alternating layers of amines and of corner sharing lead halide octahedra, exhibit dielectrically confined bound excitonic states that are ideal for light emitting diodes (LEDs). HOIS-based deep blue LEDs are rarely reported, in which cases HOIS is usually deposited between electron and hole transport layers. Here, in the quest of suitable 2D HOIS for single layer LEDs (SLLEDs), we report on the synthesis and characterization of (4-fluoro-phenethylamine-H)2PbBr4 and its defect variations (DV), formed by nonstoichiometric synthesis. The DV thin films, deposited on conducting transparent anodes, allow for easy and simple fabrication of SLLEDs, using a Ga/In droplet cathode. The pristine iodine analogue readily provides green SLLEDs, while here only the DVs or pristine material’s mixtures with MoS2 nanosized platelets appear to function. It is suggested that the defects disrupt the long-range planar and insulating nature of the micrometric 2D HOIS crystalline platelets, thus, providing mechanisms for current flow, while the excitonic recombination half times are not affected by the defects. The organic 4-fluoro-phenethylamine enhances the EL functionality of the DVs compared to other amines because of the fluorine repulsion among the amine tails, leading to stable, weakly bound, organically decorated 2D inorganic sheets. It is expected that this work will provide incentive for utilizing HOIS DVs, being compatible with large scale synthesis.