Multispectral Colloidal Quantum Dot Infrared Detectors

Nontechnical Description Infrared detectors and imagers can resolve optical images in low-visibility or obstructed environments, such as smoke, mist, and fog. While infrared technology is often associated with military activity or astronomy, modern households typically have multiple infrared sources and detectors utilized for signaling, such as in the common TV remote, communicating with a sensor in the TV through infrared radiation. Used for imaging, an infrared camera detects reflected light invisible to a regular camera for applications in space exploration and agriculture, or captures heat signatures that are useful for search-and-rescue operations (fire-fighters), surveillance and in self-driving cars. In this regard, multispectral infrared photodetection, a collection of light across multiple spectral wavelength bands, has gained attention due to its potential to improve object identification by analyzing spectral information and capturing details about an object's temperature, composition, and structural properties, which is useful in fields like gas detection, remote sensing and medical diagnostics. Traditional multispectral infrared photodetectors present technical challenges such as high fabrication complexity, high fabrication cost, requirement for cryogenic cooling and low production yield, limiting their widespread adoption. The proposed project seeks to develop a disruptive photodetector technology that offers significant advantages over current approaches, enabling room-temperature operation and a dramatic reduction in cost. The basis of this technology is colloidal quantum dots which are nanometer sized crystals synthesized via inexpensive benchtop chemistry methods. The objective of this proposal is to use a convergence of innovative materials synthesis, device fabrication, assembly and testing to develop precisely engineered colloidal quantum dot-based multispectral pixelated infrared image sensors that will be ubiquitously utilized in a broad range of civilian and military applications. The interconnected educational objective of this proposal is to develop a broad and competitive STEM workforce (including graduate, undergraduate and K-12 students) engaged and trained in materials research and to expose the broader New York City and surrounding communities, to the field of colloids, nanoscience and optoelectronics through outreach and instruction-oriented hands-on activities. Technical Description The major challenges in realizing multispectral colloidal quantum dot photodiodes lie in the lack of efficient charge transport layers, transparent conducting electrodes across the entire infrared spectrum and suitable quantum dot processing and device fabrication strategies that allow for reliable integration with Si-based read-out integrated circuits. This project will investigate a novel infrared-transparent hybrid organic-inorganic top electrode that will enable maximal photon incidence while preventing film degradation. By using a layer-by-layer liquid phase epitaxial fabrication approach, reliable, reproducible and compact colloidal quantum dot film deposition and facile charge transport within the photoactive layer will be achieved. Novel charge transport layers will be investigated that will enable fast devices with low dark currents through rapid and efficient charge extraction. These studies will generate fundamental understanding of carrier transport, recombination, and trapping of optically generated carriers in photodiodes made from narrow bandgap colloidal quantum dots. Finally, the project will develop a non-destructive light induced patterning approach to generate multipixel and multicolor infrared detectors as against conventional photoresist mediated photolithography and lift off processes which can potentially delaminate or damage the underlying colloidal quantum dot film and/or degrade the optoelectronic properties of the individual quantum dots. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.