Solution-processed finger-type organic proximity sensor with high displacement resolution

Proximity sensors are interesting devices for applications like smart homes or human-machine interfaces. This work investigates a cheap and compact short-range proximity sensor based on an organic photo detector combined with a commercial LED. Low-cost solution-processed organic materials are used, and low process temperatures at 140 °C also facilitate future integration on, e.g., plastic substrates. In particular, to avoid damage of the organic layer during the patterning process, a new organic photo detector with a semitransparent organic active layer and a transparent silver nanowire top electrode was designed. The proposed sensor can be realized by using only one shadow mask to pattern the opaque bottom electrode layer. The opaque finger-type bottom electrode not only partly shields the light emitted from below the device, but also defines the active regions with vertical electric field to generate and collect photo current. In the experiments conducted in this paper, the maximum detection distance was found to be 2 cm, whereas the lower end of the measurement range was 0.2 cm.