High Responsivity Organic Ultraviolet Photodetector Based on NPB Donor and C₆₀ Acceptor

We report fabrication and characterization of organic heterojunction UV detectors based on N,N'?bis(naphthalen?1-yl)-N,N'-bis (phenyl) benzidine (NPB) and fullerene C₆₀. The effects of different thicknesses of NPB and C₆₀ layers are studied and compared. Notably, the optimal thicknesses of electron acceptor C₆₀ and electron donor NPB are 40 nm and 80 nm, respectively. The J–V characteristic curves of the device demonstrate a three-order-of-magnitude difference when illuminated under a 350 nm UV light and in the dark at -0.5 V. The device exhibits high sensitivity in the region of 320–380 nm with the peak located around 350 nm. Especially, it shows excellent photo-response characteristic with a responsivity as high as 315 mA/W under the illumination of 192 μW?cm^?2 350 nm UV light at -5 V. These results indicate that the NPB/C₆₀ heterojunction structure device might be used as low-cost low-voltage UV photodetectors.