Conventional and Inverted UV-PDs Based on Solution Processed PFE:ZnO Active Layer

Solution processed ultraviolet photodetectors with conventional and inverted architectures with active layers composed of poly(9,9-dioctylfluorenyl-2,7-yleneethynylene) (PFE) and zincoxide (ZnO) nanoparticle hybrid are introduced. Under 1 mW/cm² illumination intensity at 365 nm wavelength and for -4 V bias and room temperature, the conventional device structure of ITO/PEDOT:PSS/PFE:ZnO/Al and the inverted device structure of ITO/PFE:ZnO/Au are yielded photoresponsivity values of 311 and 244 mA/W, detectivity values of 1.4 × 10¹⁴ and 5.1 × 10¹³ cmHz^1/2W^-1, and external quantum efficiency values of 105.6% and 82.7%, respectively. By annealing the active layer at polymer´s glass transition temperature (Tg; 60 °C) for 15 min, these values are increased to 375 and 280 mA/W, 1.6 × 10¹⁴ and 5.3 × 10¹³ cmHz^1/2W^-1, 127% and 95%, as in the above order. Performance, stability, and detectivity value differences between conventional and inverted architectures are explained electrically by impedance spectroscopy.