Performance optimization of SnO2:F thin films under quasi-vacuum laser annealing with covering a transparent PET sheet: A study using processing map

Abstract This work presents a simple and efficient quasi-vacuum laser annealing method for photoelectric performance optimization of SnO2:F (FTO) films. This method uses a transparent polyethylene terephthalate (PET) sheet to form a quasi-vacuum environment on the film surface, which was conducive to restraining the rapid loss of laser energy and thus reinforcing the laser annealing effect. It was found that the PET-assisted laser annealing effect was closely related to the transformation of the PET sheet caused by using different laser pulse energies and defocusing amounts, and thus resulted in different surface morphology features of the FTO films. The ideal laser annealing effect could be achieved only through entirely ashing the pregenerated PET carbonized residues and avoiding laser ablation of the FTO layer. Based on the established processing map, the optimal laser pulse energy and defocusing amount for PET-assisted laser annealing of the FTO films were determined to be 90 μJ and 0.6 mm, respectively. The as-obtained FTO film was confirmed to have the best overall performance with the highest average visible transmittance of 84.5%, the lowest sheet resistance of 6.8 Ω/sq and the highest figure of merit of 2.73 × 10−2 Ω−1, indicating the prominent application superiority of PET-assisted laser annealing.