Effect of Bimetallic Doping on the Optoelectronic Properties of Zeolitic Imidazolate Framework-8 (ZIF-8)

Abstract

Zeolitic Imidazolate Framework-8 (ZIF-8) stands out among other metal-organic frameworks (MOFs) for optoelectronic applications because of its large surface area, high porosity and tunable characteristics. This study examined the impact of bimetallic doping of pristine ZIF-8 with cobalt (Co) and zinc (Zn) in enhancing its performance in devices like photodetectors, solar cells, and light-emitting diodes. UV-VIS spectroscopy, FTIR and SEM were used to analyze the nanocomposites' optical and morphological properties. Optical characterization shows that co-doping enhanced the absorbance thereby reducing the transmittance to an average of 22% making the material appropriate for light-harvesting systems. In addition, bandgap energy decreased from 2.82 eV to 1.25 eV due to impurity band formation improving the optoelectronic response of the material. Furthermore, co-doping increased the refractive index from an average of 1.64 to 2.36, showing higher interactions between light and matter.  The dielectric constant was also improved by Co/Zn co-doping suggesting an increase in charge storage as well as polarization crucial for optoelectronic devices. FTIR spectroscopy revealed alterations in the chemical bonds suggesting that the Co and Zn impurities have been successfully incorporated into the ZIF structure. SEM images revealed alterations in the morphology of the composites including increased crystallite size and heterogeneity in appearance due to co-doping and the modification in their composition was confirmed by EDS spectra. Overall, these findings show that bimetallic doping of  ZIF-8 nanocomposites  with Co and Zn enhanced  the optical absorption, charge storage potential and flexibility, making them ideal for   sensors, energy harvesting, and photocatalysis