A potassium ion conducting polyblend electrolyte based on polyvinyl pyrrolidone (PVP) + polyvinyl alcohol (PVA) complexed with KBrO3 was prepared using solution cast technique. The electrical conductivity increased with increasing dopant concentration. Optical absorption studies were made in the wavelength range (200-600 nm) on pure (PVP + PVA) and KBrO3 doped (PVP + PVA) films. The absorption edge was observed at 5.13 eV for undoped (PVP + PVA) while it ranged from 4.88 to 5.0 eV for differently KBrO3-doped samples. The direct band gaps for undoped and KBrO3 doped (PVP + PVA) films were found to be, respectively, 5.05 and 4.95, 4.86 and 4.90 eV while the indirect band gaps were 5.03 and 4.88, 4.79 and 4.83 eV, respectively. The absorption edge and the band gaps moved towards lower energies as the dopant concentration was increased up to 20 wt% of the dopant. For further increase in dopant concentration these values started increasing again. This is explained in terms of formation of charge transfer complexes between the dopant and the host matrix. The thermal properties of these films were investigated with differential scanning calorimetry (DSC). The variation in film morphology is examined by scanning electron microscopic examination. (c) 2005 Elsevier Ltd. All rights reserved.