Microstructure and optical properties of Ni2+ doped PVA for optoelectronic devices

Abstract

Different wt.% of Ni2+- doped Poly (vinyl alcohol), PVA, films are synthesized by a low-cost casting method. XRD, SEM and FTIR spectroscopy are used to study the microstructure of the composite samples. The degree of semi-crystallinity for all Ni2+-doped PVA (NPVA) and pure PVA films decreases and the amorphous order dominated in 3.7 wt% Ni2+-doped PVA (NPVA5) film as established by studying the spectroscopy of XRD and FT-IR. The increment of the Ni2+-doping level in PVA led to a formation of non-homogeneous particle size with an average value range from 1.03 μm to 4.47 μm for 0.027 wt% Ni2+-doped PVA (NPVA1), and NPVA5 films, respectively. UV–Vis-IR transmittance and absorption spectroscopies are specified for measuring the optical parameters. The indirect energy gap (Eig) decreases to 4.85 eV for NPVA5 film, and the direct energy gap, Eg, to 1.36 eV for the same sample. However, owing to the complex construction between Ni2+-ions and the matrix of PVA, the transition strength (Ed), the indices of refraction (n, n∞), and oscillator wavelength (λ0) increase, while the excitation energy (Es) decreases with further wt.% of Ni2+-ions. Due to the optical properties of the films, they are suitable to be inserted in different optoelectronic applications.