Robust structural, optical and thermal properties of stannic oxide nanoparticles incorporated polyindole nanocomposite as an efficient emissive layer material for OLED application

In this research, polyindole (PIN) nanocomposites reinforced with stannic oxide (SnO₂) were synthesized using a straightforward in situ chemical oxidative polymerization technique. Fourier transform infrared spectroscopy (FTIR) was used to identify the chemical bonding of SnO₂ in the PIN, indicated by the characteristic peak around 602 cm⁻¹. The addition of SnO₂ nanoparticles improved the crystallinity of PIN matrix, as confirmed by X-ray diffraction (XRD) and average crystallite size for 15% PS was estimated to be 9 nm. 15% PS showed an enhanced optical bandgap of 2.78 eV and a reduced refractive index of 2.07 compared to pristine PIN. Uniformly dispersed SnO₂ nanoparticles on the surface PIN matrix were observed via field emission-scanning electron microscopy (FESEM). X-ray electron spectroscopy (XPS) analysis confirmed the formation of the 15% PS nanocomposite by revealing the presence of all elements (C, N, Sn and O) and their chemical oxidation states (C1s, N1s, O1s, Sn 3d_3/2 and Sn 3d_5/2) in the corresponding spectra. The thermal stability of pure PIN improved by 7% with SnO₂ nanoparticle incorporation. The 15% PS nanocomposite exhibited the highest PL intensity, with strong emissions at 431 nm and 481 nm, and weaker emissions at 628 nm, 680 nm, 718 nm, and 757 nm. The colour purity of 15% PS is estimated to be 2.8% (close to zero) which indicates that the emission is nearly white. These properties highlight its potential as an emissive layer for white light emission in organic light emitting diodes (OLEDs).