Extraordinarily high ultraviolet photodetection by defect tuned phosphorus doped ZnO thin film on flexible substrate

Phosphorus (P) doped zinc oxide (ZnO) thin film has skillfully been deposited on flexible substrate using radio frequency sputtering technique at room temperature under controlled oxygen ambient to tune its point defects. P doped ZnO film shows a very high ultraviolet (UV) photosensitivity with responsivity and detectivity values of 23.5 mA/W and 1.86$\times$10¹³ Jones respectively as compared to the values of 0.073 mA/W and 2.56$\times$10¹⁰ Jones respectively for pristine ZnO. Incorporation of P dopant under controlled oxygen ambient results in a very low dark current value due to acceptor-donor compensation leading to an unprecedentedly ultra-high photo-to-dark current ratio of 2.15×10⁵ under 350 nm illumination. A photosensitivity under repetitive flat and bending conditions has been attained. Further, photoresponse towards a low intensity UV illumination of power 29 μW/cm² has been noted with a photo-to-dark current ratio of 3.88$\times$10³ indicating an excellent photodetection efficiency of the P doped ZnO film.