Use of additives in porphyrin-tape/C60 near-infrared photodetectors

We demonstrate organic heterojunction photodetectors sensitive to wavelengths lambda > 1500 nm based on a solution processed Zn-porphyrin-dimer donor layer that includes phenyl-C-61-butyric acid methyl ester (PCBM) and/or 4,4'-bipyridyl (Bipy) additives, and an evaporated C-60 acceptor layer. The inclusion of PCBM results in up to a 20-fold increase in differential resistance, while the inclusion of Bipy results in up to a 100% increase in external quantum efficiency (EQE) compared to devices lacking additives. The devices have peak specific detectivities of D* = 8.8 +/- 0.2 x 10(11) Jones (EQE = 3.6 +/- 0.1%) at lambda = 1130 nm, and D* = 8.2 +/- 0.2 x 10(10) Jones (EQE = 10.5 +/- 0.2%) at lambda = 1400 nm. The maximum external quantum efficiency at lambda = 1400 nm is 13.5 +/- 0.3%, approximately double that of previously reported organic near infrared detectors. (C) 2011 Elsevier B.V. All rights reserved.