Incorporating Aluminum Plasmonic Nanohemisphere Arrays into Organic Ultraviolet Photodetectors for Improved Photoresponse

Aluminum nanostructures, which support surface plasmon resonances in the UV spectral range, were incorporated into conventional organic UV photodetectors with a structure of indium tin oxide (ITO)/poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS)/poly(9,9-dioctylfluorene-alt-bithiophene) (F8T2):[6,6]-phenyl-C71-butyric acid methyl ester (PC71BM)/LiF/Al. Nanohemisphere arrays (NHSAs) were imprinted into the top surface of the soft organic active layer, thus transferring the pattern to the subsequently thermally deposited layers of LiF and Al. NHSA-top devices and flat-top control devices were investigated by 3-dimensional finite-difference time-domain (3D-FDTD) electromagnetic simulations. Improved UV active layer absorbance and enhanced electric fields in the nanohemispheric region at the top of the active layer were shown for devices with the NHSA-top. The impact of the NHSA-top was found to be more significant for devices with thin active layers and to gradually decrease with increasing active layer thickness. Fabricated NHSA-top devices with thin active layers exhibited improved photoresponse in terms of external quantum efficiency, specific detectivity and on–off response speed compared to flat-top devices under 330 nm illumination and 0 to −1 V bias. The method developed in this work provides a versatile and effective way to incorporate plasmonic nanostructures into optoelectronic devices to enhance device performance.