Polyaniline (PAn) has been successfully prepared by photopolymerization of dimeric aniline via photocatalytic reaction with Ru (bpy) ₃²⁺. We investigated template photopolymerization in the presence of DNA in order to prepare PAn with longer π-conjugation length. The PAn/DNA complex formed in an aqueous solution was water-soluble, leading to improve the processability of PAn for devices. The PAn/DNA complex film containing Ru (bpy) ₃²⁺ shows red light emission by applying a voltage. The device, i.e ., Al/PAn-DNA complex+Ru (bpy) ₃₂₊/ITO, emitted light over a bias voltage of 7 V, and the luminance increased with increasing bias voltage. A maximum luminance of 1500 cd/m² was observed.