Lateral Organic Semiconductor Photodetector. Part I: Use of an Insulating Layer for Low Dark Current

The thin flexible, lightweight nature of organic semiconductor devices makes them a prime candidate for medical imaging applications such as rugged X-ray imagers for use in hospitals (i.e., immune to minor drops or shocks) or even curved X-ray imagers for specialized imaging modalities of the future (e.g., compression free breast imaging). However, the performance of these organic sensors is not yet comparable with current technology (amorphous silicon) in particular owing to high dark currents. Here we show that the use of an insulator material, such as polystyrene, can dramatically improve the dark current performance of the organic photoconductor without compromising the device speed. Consequently, we are able to operate the sensor under high bias to achieve significant improvements in the critical parameters for image sensors such as photo-to-dark current ratio, sensitivity, dynamic range, and transient speed. Our work has the potential to expedite the adoption of organic semiconductor technology for a variety of digital imaging applications especially in the field of low-cost, portable biomedical equipment.