Impact of metal doping on the electrical and optical properties of AgI2 QDs: A DFT study

Abstract

This study investigates the electronic conductivity tensor (ECT) of silver iodide (AgI₂) quantum dots (QDs) and the impact of metal impurities (Cu, Ni, Zn) on their optoelectronic properties, utilizing density functional theory (DFT) and the Kubo-Greenwood formalism. Pristine AgI₂ exhibits a calculated band gap of 2.2 eV and an Ag-I bond length of 2.83 Å, demonstrating anisotropic electrical conductivity. Singularities in the imaginary part of the ECT at 4.3 and 5 eV indicate resonant responses to specific frequencies, potentially enhancing optical conductivity as well as absorption and emission. The incorporation of Cu as Ag_CuI₂ results in a modified ECT spectrum with peak shifts and increased imaginary components, suggesting improved optical conductivity and sensitivity to electric fields, which is beneficial for optical sensor applications. Furthermore, doping with Ni and Zn was also explored. Bond lengths for Ag-Ni, I-Ni, Ag-Zn, and I-Zn are 3.19 Å, 2.98 Å, 3.18 Å, and 3.09 Å, respectively, while band gaps for Ag_NiI₂ and Ag_ZnI₂ are 1.49 eV and 1.68 eV, respectively, which are lower compared to AgI₂. Ag_NiI₂ and Ag_ZnI₂ exhibited enhanced ECT, with Ag_ZnI₂ showing the most significant improvement in tensor elements. Overall, the findings highlight the significant tunability of AgI₂ QD optoelectronic properties through impurity engineering, providing pathways for tailoring materials for specific applications in optoelectronics and solar energy.