The temperature dependences of photoluminescense of poly(9,9-dioctylfluorene) (F8) thin films with three different backbone conformations controlled by thermal treatments, such as as-coated, annealed and crystallized thin films have been studied. The polymer forms disordered phase in the as-coated film, and ordered phase in the crystallized film. It is found that the strength of electron-phonon interaction, which is evaluated from Huang-Rhys factors, is enhanced with increasing temperature in all the films. The film annealed at around glass-transition temperature shows stronger temperature dependence of Huang-Rhys factor, suggesting that the annealed film consists of different phases such as disordered and beta-phase. (c) 2005 Elsevier B.V. All rights reserved.