Optical characteristics of synthetic Cu2+ complex films derived from 4-chloro-N-(3-(hydroxyimino) butan-2-ylidene) benzohydrazide for optoelectronic and photovoltaic applications

•This study focuses on the formation and properties of Cu2+ complexes.•The band gap of 1.76 eV verifies its suitability to photovoltaic applications.•The prepared Cu2+ complexes be used in optoelectronics applications. This study focuses on the creation and characterisation of Cu2+ complexes using the ONN tridentate chelating ligand, 4-chloro-N'-(3-(hydroxyimino) butan-2-ylidene) benzohydrazide (H2CIB). Synthetics were structurally investigated using a variety of elemental, molar conductivity, magnetic moment measurements and spectroscopic (1D-NMR, UV−Vis, FT-IR, and E-mass) tools as well as theoretically. The data from these analyses revealed that the hydrazone-oxime ligand acted as a mono-negative or neutral tridentate chelator, bonding the Cu2+ ions through the enolo/ketono carbonyl oxygen, protonated oximatic nitrogen, and azomethine nitrogen atoms, resulting in the formation of a square plane structure. In addition, the optical properties of these synthetics were studied. Based on the measured film reflectance, the index of refraction and extinction (k)/absorption (α) coefficient were determined through Kramers-Kronig (K-K) analysis. The optical band gap Eg value is estimated experimentally by different methods. The hydrazone-oxime ligand has the highest value of Eg where the complexes have Eg = 1.76, 1.83 and 1.76 eV for Cu2+- HCIBCuNO3, HCIBCuCl, and H2CIBCuSO4 samples, respectively. The Eg of CdSe is 1.74 eV which is very close to the Eg value of HCIBCuNO3, and H2CIBCuSO4. Therefore, the HCIBCuNO3, and H2CIBCuSO4 can replace the CdSe in all photovoltaic applications, photosensors and solar cells. With the help of n and k values the complex dielectric constant (ε⌣=εr+iεi)) and conductivity (σ⌣=σr+iσi) have been investigated over the whole spectral range. Furthermore, the first (χ(1)) and third (χ(3)) orders of nonlinear optical susceptibilities and the non-linear index (n2) of refraction has been estimated. According to the estimated values of χ(1), χ(3) and n2 the HCIBCuNO3, HCIBCuCl, and H2CIBCuSO4 can be considered as competitors to be used in optical switching gadgets, optical modulators, and optical signal processing. [Display omitted]