A comparative study of microstructures on the photoelectric properties of tungsten trioxide films with plate-like arrays

Abstract WO 3 plate-like array film was grown on the FTO electrodes by a simple hydrothermal method. In order to change the microstructures of the WO 3 films, the as-grown films were further post-heat treated in air and in H 2 , respectively. The photoresponse characteristics of the as-prepared WO 3 films are investigated in the gas phase, and to explain the slow decay of the photocurrent of WO 3 , the electron trapping effect is proposed. We found that both of the phase structures and oxygen vacancies had great influences on the photoresponse characteristics of WO 3 films. For the three WO 3 films, the photocurrent decreased significantly with the distortion of the octahedra which were the building blocks of the various crystal structures and with the decreasing of oxygen vacancy concentration. The untreated-WO 3 shows 2.5 times higher photocurrent intensity than hydrogen-treated WO 3 and the hydrogen-treated WO 3 shows 17 times higher photocurrent intensity than air-treated WO 3 . The experimental results revealed the influence of phase structure on the photoelectric performance of WO 3 was far greater than that of oxygen vacancy. We also found that the hydrogen-treated WO 3 exhibited excellent infrared photoresponse property, which was 20 times higher than that of the pristine WO 3 . This was attributed to the existing large number of oxygen vacancies yielding extended energy states which often formed a continuum extending to and overlapping with the conduction band (CB) edge.