Organic luminescent materials have garnered substantial attention within the scientific community owing to their notable attributes, encompassing cost-effectiveness, solution processability, mechanical flexibility, and easily adjustable optoelectronic properties. This multifaceted appeal has propelled their extensive adoption across a spectrum of applications, ranging from organic light-emitting diodes (OLEDs) and organic solid-state lasers (OSSL) to fluorescence imaging methodologies. Nevertheless, the advancement of organic electrically pumped lasers encounters significant hurdles. Organic gain media frequently grapple with challenges such as restricted charge carrier mobility, extended lifetimes of triplet states and polarons, broad absorption profiles, and inadequate stability, all of which pose substantial barriers to the practical realization of these laser systems. In response to these challenges, this study endeavors to introduce voluminous spatial hindrance groups as a prospective solution. These groups are strategically integrated to hinder intermolecular interactions among luminescent molecules, thereby alleviating the inherent luminescent quenching effects of the materials. This intervention not only augments luminescent efficiency but also fortifies the material's stability, addressing pivotal concerns within the discipline. The research methodology encompasses the design and synthesis of two distinct fluorene-based oligomers, namely HTF and ITF, each distinguished by unique spatial configurations. A meticulous examination of their amplified spontaneous emission (ASE) characteristics is conducted under diverse test conditions, incorporating dependencies on annealing temperature and film thickness. The minimum ASE thresholds for HTF and ITF are meticulously determined to be 6.67 and 12.35 µJ/cm², respectively. Furthermore, comparative analyses between HTF and ITF illuminate the distinctive performance attributes of each oligomer. Notably, HTF exhibits superior thermal stability, diminished temperature dependence, and reduced reliance on film thickness in contrast to ITF. Additionally, an evaluation of dibromo-substituted derivatives unveils variable degrees of negative impact on the ASE characteristics of both oligomers following bromine atom substitution, with ITF demonstrating a more pronounced susceptibility. Overall, this comprehensive investigation not only yields valuable insights into the structural design and performance modulation of organic laser gain media but also presents promising avenues for optimizing their efficiency and stability within the domain of optically pumped organic lasers.

Key words: organic laser, amplified spontaneous emission, gain media, steric hindrance, fluorine