Characterization of annealed N,N′-diphenyl-N,N′-di-p-tolylbenzene-1,4-diamine nanostructured thin films
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Exploring new efficient derivatives of polyphenylamines to act as a hole transport layer (HTL) in organic light emitting diodes is a global demand. Herein, we introduce N,N′-diphenyl-N,N′-di-p-tolylbenzene-1,4-diamine (NTD) as a potential HTL. Nanostructured films of NTD with thickness 75 nm are spin coated. Subsequently, these films are manipulated via annealing process and characterized using different techniques. The fluorescence spectrophotometer reveals that NTD film undergoes a Stokes shift of 3546 cm−1 upon excition using a beam of wavelength of 365 nm. The X-ray diffraction analysis shows that NTD films consist of nanoparticles (NPs) with an average crystallite size of 33.43 nm. Upon annealing the films at temperatures of 373 and 423 K, the size of the NPs has climbed to 40.22 and 46.45 nm respectively. The UV/Vis spectroscopy indicates that the NTD films have transmittance values greater than 87% in the visible region, which are enough to meet the requirements of the HTL materials in optoelectronic devices. Additionally, the Urbach and bandgap energies are declined with the annealing temperatures. This is due to the dramatically ordering of the NTD NPs with the annealing process. Impedance spectroscopy is also conducted in the frequency range from 500 Hz to 5 MHz at temperatures of 303, 373, and 423 K. Further, the Nyquist plots (Zim vs. Zre) are fitted to an equivalent circuit using EC-Lab software. The impedance is descended by increasing the annealing temperature. On the same approach, the charge transfer resistance (Rct) dropped from 69.61 to 23.27 kΩ when the temperature is risen from 303 to 423 K, which confirms the semiconductor behavior of the NTD films.
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All authors declare that there are not any relationships or interests that could influence or bias the submitted work.
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