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

We demonstrate organic heterojunction photodetectors sensitive to wavelengths λ > 1500 nm based on a solution processed Zn–porphyrin-dimer donor layer that includes phenyl-C61-butyric acid methyl ester (PCBM) and/or 4,4′-bipyridyl (Bipy) additives, and an evaporated C60 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 × 1011 Jones (EQE = 3.6 ± 0.1%) at λ = 1130 nm, and D∗ = 8.2 ± 0.2 × 1010 Jones (EQE = 10.5 ± 0.2%) at λ = 1400 nm. The maximum external quantum efficiency at λ = 1400 nm is 13.5 ± 0.3%, approximately double that of previously reported organic near infrared detectors.