Inkjet printed organic detectors with flat responsivity up to the NIR and inherent UV optical filtering

The use of printing technologies is widely recognized to be a major advantage for the deployment of large-area organic electronics and there is still plenty of room for exploring new strategies to exploit printing of solution processable conductors and semiconductors. In this paper, we show for the first time how an additive layer-by-layer deposition, achieved through inkjet printing, enables the fabrication of broadband organic photodetectors with a flat responsivity spectrum extending to the near-infrared (NIR). The use of narrow bandgap polymers enables light detection up to 1.1 μm. By controlling the photoactive layer thickness in a range between 150 nm and 4 μm, we could filter the contribution from UV and Vis absorption to the photocurrent, while keeping light detection in the NIR. The visible detection efficiency decreases of a 70% at 425 nm for thicknesses going from 250 nm up to 2 μm, while the NIR detection decreases only of 31% at 950 nm, and increases of 26% at 1020 nm. This photoactive layer thickness dependent UV–vis optical filtering enables the control over the shape of the responsivity spectra.