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

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 mu m to 4.47 mu m 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 (E-ig) 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 (E-d), the indices of refraction (n, n(infinity)), and oscillator wavelength (lambda(0)) increase, while the excitation energy (E-s) 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.