Fabrication of a Homogeneous, Integrated, and Compact Film of Organic-Inorganic Hybrid Ni(en)₃Ag₂I₄ with Near-Infrared Absorbance and Semiconducting Features

The organic-inorganic hybrid crystal Ni(en)₃Ag₂I₄ (where en represents 1,2-ethylenediamine) crystallizes in hexagonal space group P6₃, in which the AgI₄^3- tetrahedra connect into a diamondlike inorganic framework via sharing of the vertex and the Ni(en)₃²⁺ octahedra fill in the pores of the framework. UV-vis-near-IR (NIR) spectroscopy disclosed that this hybrid shows intense NIR absorbance centered at ca. 870 nm, and the variable-temperature conductivity measurement revealed that the hybrid is a semiconductor with E_a = 0.46 eV. The electronic band structure of Ni(en)₃Ag₂I₄ was calculated using the density functional theory method, indicating that the NIR absorbance arises from d-d transition within the Ni²⁺ cation of Ni(en)₃²⁺. The homogeneous, compact, and transparent crystalline film of Ni(en)₃Ag₂I₄ was fabricated via a secondary seed growth strategy, which has promising application in NIR devices.