High photoresponse from solution processed conventional and inverted ultraviolet photodetectors

The optical and electrical properties of conventional and inverted type ultraviolet photodetectors (UVPDs) with active layers of poly(9,9-dioctylfluorenyl-2,7-ylenethynylene (PFE), N ,N ′ -bis-n-butyl-1,4,5,8-naphthalenediimide (BNDI), and zincoxide (ZnO) are introduced. Optimized devices showed high photoresponse, external quantum efficiency (EQE), and detectivity (D*) values. Under 365 nm 1 mW/cm2 , the conventional device (ITO/PEDOT:PSS/[(PFE:BNDI) (3:1):8 wt% ZnO]/Al) and the inverted device (ITO/[(PFE:BNDI)(3:1):8 wt% ZnO]/Au) gave photoresponsivities of 515 mA/W and 316 mA/W, D* of 1.12 x 10 14 Jones and 0.71 x 10 14 Jones, and EQE of 174% and 107%, respectively. Annealing the devices at polymer’s glass transition temperature (Tg 60 ◦ C), enhanced these values to 651 mA/W and 343 mA/W, 1.33 x 10 14 Jones and 0.73 x 10 14 Jones, and 221% and 116%, respectively. Furthermore, high performance, sensitivity, D*, and EQE values of different architectures were examined by impedance spectroscopy.