Amorphous glassy regions in organic electronic devices play a pivotal role in the final performance. While tuning the properties of these regions normally relies on modifying the chemical nature of the organic semiconductor, the effect of exploring the wealth glassy states attained varying the kinetic pathway to obtain them has hitherto remained largely unexplored. In this contribution, a typical semi-conducting polymer, poly(9,9-di-n-octylfluorenyl-2,7-diyl (PFO), is submitted to different thermal histories, including i) annealing in the melt to trigger the transformation from isotropic liquid to liquid crystal and vice versa and; ii) varying the cooling rate to transform the melt into a glass; so called “vitrification” or “glass transition”. In this way, the glass the fictive temperature, Tf, the metric used to define the glass thermodynamic state, can be spanned over several tens of Kelvin. Such large variation significantly impacts PFO photoluminesce properties, a result bearing profound implications on tuning the photovoltaic performance of the electronic device.