Polyfluorene copolymer /Al Schottky junction for UV-A photodetector with relatively high stability and photocurrent density

Abstract We report on the selective detection of UV-A region by using a single layer of a conjugated copolymer forming a Schottky junction in connection with Al cathode. The structure of the prepared UV detector is ITO/PEDOT:PSS/poly[9,90-dioctyl-fluorene-2,7-diyl]-copoly[diphenyl-p-tolyl-amine-4,40-diyl] (BFE)/Al fabricated by simple solution processed method. Under the UV-365 nm illumination with 5 mW/cm 2 irradiation intensity through semi-transparent Al cathode, the fabricated device exhibited a photo-to-dark current ratio of about 102 at bias voltage of -5 V. The photodetector shows a maximum spectral responsivity of 38 mA/W, corresponding to the maximum detectivity (D*) of ∼ 109 Jones, at 380 nm and -5 V. Based on experimental results, the cut-off frequency of the photodetector is more than two orders of magnitude. This work proposes a cost-effective and simple structure organic photodetector exhibiting a good combination of air stability in both air environment and UV exposure, spectral selectively in UV-A region, photo responsivity, linear dynamic range, and frequency response.