<p>Poly(9,9-di-n-octylfluorenyl-2,7-diyl) (PFO) polymer-based light-emitting diodes (PLEDs) were synthesized using toluene and tetrahydrofuran (THF). The PFO-based PLEDs were deposited onto polyaniline (emeraldine base) (PANI)/ITO using the doctor blade technique, followed by structural, morphological, topographical, and electrical properties of the polymer films were examined. The chemical bonds, absorbance and photoluminescence (PL) spectra of the samples were also investigated, and the effect of the precursor solvent on these characteristics of PFO-based PLEDs was studied, revealing that the toluene–PFO film (higher viscosity and surface roughness) displayed a higher PL intensity. Polarity affects the emission wavelength by causing a red shift in the PL spectra to the THF–PFO film, which is attributable to its higher polarity index. Vapor pressure was shown to cause switching of the PL intensity for both PFO-based PLEDs. The results also revealed poor color quality in the green emission at 2.2 to 2.4 eV; thus, viscosity, vapor pressure and polarity of the solvents strongly affect the characteristics of PFO thin films. The precursor solvent for the synthesis of PFO can be considered a tuning factor for the emission of PFO-based PLED.</p>