The thermal stability of the poly(2,7-carbazole) derivative (PCDTBT) is investigated. UV visible absorption spectra and X-ray photoelectron spectroscopy data demonstrate that the electronic structure of PCDTBT is stable in air at annealing temperatures up to 150 degrees C and in N-2 even after exposure to temperatures up to 350 degrees C. Field-effect transistors fabricated with PCDTBT show stable characteristics and hole mobility up to 150 degrees C (air) and 350 degrees C (N-2).