New OLEDs Based on Zirconium Metal-Organic Framework

The search for new smart-materials in solid-state light-emitting applications, like hybrid organic-inorganic light-emitting devices (OLEDs), has seen an intense growth in the recent years. Among all the possibilities, metal-organic frameworks (MOFs) have emerged as promising smart materials due to their chemical and structural properties. Herein, for the first time, the use of a Zr-based MOF (Zr-NDC, NDC = dimethyl 2,6-naphthalenedicarboxylate) as electroluminescent active material in OLED devices is reported. The results indicate that, independently of the properties of the polymer used to form the emissive layer, the OLED emission is due to radiative electron and hole recombination in the MOF. A tuning of the optoelectronic properties of the device by incorporating Coumarin 153, (C153) and 4-(Dicyanomethylene)-2-methyl-6-(4-dimethylaminostyryl)-4H-pyran, into the MOF pores is demonstrated. Using different MOFLED architectures, and MOF composition, it is possible to elucidate the photoluminescence and electroluminescence mechanisms, providing the clues for further improvements. It is observed that the current density as well as the electroluminescent behavior depends on the dopant fluorophores. It is also shown that defects within the Zr-MOF play a role in the OLED optoelectronic properties. The results clearly demonstrate the potential of MOFs as new tunable electroluminescent materials for OLED applications.