Fabrication and investigation of PMMA-doped 1, 3, 5-triphenylbenzene (TPB) thin film's structural, optical, and electrical properties for optoelectronic devices

Abstract

In this experimental work, triphenylbenzene/polymethylmethacrylate (TPB/PMMA) based thin films were deposited using a spin coating to examine their structural, optical, and electrical properties. The deposited thin film has a crystalline nature with an average crystalline size of 27.12 nm, and a dislocation density of 7.1 × 10−4 nm−2. The absorption spectra of TPB, PMMA, and TPB-PMMA films lie in the range of 200 nm–500 nm with an optical bandgap of 3.85 eV, for TPB-PMMA. The PL spectra of pure TPB thin film give a constant emission at 360 nm, which is independent of the excitation wavelength in the range of 310 nm–340 nm. The excitation-dependent behaviors for both pure TPB and TPB-PMMA were observed in terms of intensity that first increases and gives maximum intensity for the excitation wavelengths of 328 nm and 315 nm, respectively. From CIE coordinates, it was observed that the TPB-PMMA thin film gives a constant deep blue emission. The effect of TPB-PMMA percentage was examined with the help of IV studies, and at 20 % TPB: PMMA, the presence of more TPB molecules was observed resulting in a smaller distance between molecules and a larger number of available paths for current flow. Further, with a rise in temperature from 303K to 353K, the thermal stability of the TPB-PMMA thin film was excellent, and it kept the ohmic behavior. The examined optical bandgap of TPB-PMMA thin film falls within the range that is appropriate for OLEDs with emission in the blue region. In addition, the excellent structural and electrical properties of TPB-PMMA make it a suitable candidate for optoelectronic devices.