We fabricate an ultraviolet photodetector based on a blend of poly
(N-vinylcarbazole) (PVK) and 2-tert-butylphenyl-5-biphenyl-1,3, 4-oxadiazole (PBD)
using spin coating. The device exhibites a low dark current density of 2.2 \times
10?3 \muA/cm2 at zero bias. The spectral response of the device shows a narrow
bandpass characteristic from 300 to 355 nm, and the peak response is 18.6 mA/W
located at 334 nm with a bias of -1 V. We also study the performances of
photodetectors with different blend layer thicknesses. The largest photocurrent
density is obtained with a blend of 90 nm at the same voltage.