Recent advances in organic photodiodes (Conference Presentation)

Although the detection of photons is ubiquitous, man-made photon detectors still limits the effectiveness of applications such as light/laser detection, photography, astronomy, quantum information science, medical imaging, microscopy, communications, and others. The performance of the technologically most advanced detectors based on CMOS semiconductor technology has improved during the last decades but at the detriment of increased complexity, higher cost, limited portability and compactness, and limited area. On the other hand, nature has produced a relatively simple detector with remarkable properties: the human eye. The exploration of new paradigms in photon detection using new material platforms might therefore provide a path to further challenge the frontiers of applications enabled by light. In this talk, we will report on the realization of solution-processed organic semiconductor visible spectrum photodetectors with a high specific detectivity above 1014 Jones, at least an order of magnitude larger than values found in photodiodes based on silicon. These detectors demonstrate a sub-pA current under reverse bias in the dark, making them suitable for detecting very low levels of light. The small dark current under reverse bias allows the characterization of these devices over 9 orders of magnitude of increasing light irradiance. The detectors are based on the device structure: tin-doped indium oxide / ethoxylated polyethylenimine / poly(3-hexylthiophene) : indene C60 bisadduct / molybdenum oxide / silver and present a path toward fabrication on flexible substrates. We will show that these detectors can operate over a large dynamic range in the self-powered photovoltaic mode where the light produces a photovoltage that can be measured directly without any external bias source. We believe that large-area flexible photodetectors with detectivity values comparable to or better than those displayed by silicon-based photodiodes will enable a wide variety of applications from the detection of radiation to non-planar imaging arrays.