However, it is not easy to process largearea, homogeneous thin OPD films by conventional coating techniques, such as spin-coating. Using slot-die coating of the active organic photodetector materials, we have developed a cost-effective, scalable photodetector array technology. We demonstrate its use in a high-resolution fingerprint detector with a thin form factor that ultimately would allow users to securely unlock their phone or open user-specific apps by touching anywhere on the display screen.The fingerprint scanner is based on three main building blocks (Figure 1a for a schematic of the fingerprint scanner, Figure 1b for the circuit diagram, and Figure S1, Supporting Information, for a full stack cross section). The backplane is a dual-gate self-aligned oxide thin-film transistor (DG-SA TFT) array, described and characterized elsewhere. [12] The second (bottom) gate is typically used to increase the transistor current for a given geometry and voltage. Here, it also acts as a light shield of the oxide semiconductor in case of backside exposure, thereby increasing device stability. [13] The DG-SA TFT exhibits a low off-current with values below 1 pA, lower than the off-currents of amorphous and low-temperature polycrystalline silicon transistors. This is due to the large bandgap of IGZO (≈3 eV) that results in a low leakage current. The field-effect mobility of our TFTs is 15 and 16 cm 2 V −1 s −1 for the top and bottom gate operation, respectively. In so-called dual gate mode, that is, V g top = V g bottom , the effective mobility is equivalent to 35 cm 2 V −1 s −1 . The values can be compared to a-Si TFTs (≈1 cm 2 V −1 s −1 ) and LTPS TFTs (≈100 cm 2 V −1 s −1 ). The frontplane consists of organic photodiodes (OPDs). The technology is based on a bulk heterojunction (BHJ) structure of a p-type (donor) polymer, polyPCDTBT, and an n-type (acceptor) fullerene, 6,6-phenyl-C61-butyric acid methyl ester, PCBM. The blend is deposited by slot-die coating, resulting in a 280 nm film. Semitransparent IGZO (bottom) and MoOx/Ag (top) electrodes are used. The a-IGZO is deposited on top of an opaque MoCr layer. This is done to prevent direct detection from the backlight, so only light that is reflected from objects on top of the imager array is measured by the OPD. The sensor is coupled with an optically transparent thin-film encapsulation to avoid moisture ingress that degrades the OPD materials. [14] The fabrication processes are compatible with flat panel display manufacturing lines. Details on the Organic photodetectors (OPDs) have attracted much attention in recent years, due to their promise in large-area light sensing applications. Here, high-resolution slot-die-coated large-area bulk heterojunction organic photodiode (OPD) arrays are reported. The OPD uses a novel electron transport layer, indium gallium zinc oxide in combination with a molybdenum oxide top-electrode. Together, these effectively reduce dark current densities to very low levels of ≈10 −7 mA cm −2 at −2 V. The OPDs show linear behavior in a wide rang...