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Abstract Space missions critically rely on sensors that operate throughout the near‐ to longwave infrared (NIR – LWIR, λ = 0.9–14 µm) regions of the electromagnetic spectrum. These sensors capture data beyond the capabilities of traditional optical tools and sensors, critical for the detection of thermal emissions, conducting atmospheric studies, and surveillance. However, conventional NIR‐LWIR detectors depend on bulky, cryogenically cooled semiconductors, making them impractical for broader space‐based applications due to their high cost, size, weight, and power (C‐SWaP) demands. Here, an IR photodetector using a solution‐processed narrow bandgap conjugated polymer is demonstrated. This direct bandgap photoconductor demonstrates exceptional infrared sensitivity without cooling and has minimal changes in figures‐of‐merit after substantial ionizing radiation exposure up to 1,000 krad – equivalent to three years in the most intense low Earth orbit (LEO). Its performance and resilience to radiation notably surpass conventional inorganic detectors, with a 7.7 and 98‐fold increase in radiation hardness when compared to epitaxial mercury cadmium telluride (HgCdTe) and indium gallium arsenide (InGaAs) photodiodes, respectively, offering a more affordable, compact, and energy‐efficient alternative. This class of organic semiconductors provides a new frontier for C‐SWaP optimized IR space sensing technologies, enabling the development of new spacecraft and missions with enhanced observational capabilities. 

Abstract Phosphate oxyanions play central roles in biological, agricultural, industrial, and ecological processes. Their high hydration energies and dynamic properties present a number of critical challenges limiting the development of sensing technologies that are cost‐effective, selective, sensitive, field‐deployable, and which operate in real‐time within complex aqueous environments. Here, a strategy that enables the fabrication of an electrolyte‐gated organic field‐effect transistor (EGOFET) is demonstrated, which overcomes these challenges and enables sensitive phosphate quantification in challenging aqueous environments such as seawater. The device channel comprises a composite layer incorporating a diketopyrrolopyrrole‐based semiconducting polymer and a π‐conjugated penta‐t‐butylpentacyanopentabenzo[25]annulene “cyanostar” receptor capable of oxyanion recognition and embodies a new concept, where the receptor synergistically enhances the stability and transport characteristics via doping. Upon exposure of the device to phosphate, a current reduction is observed, consistent with dedoping upon analyte binding. Sensing studies demonstrate ultrasensitive and selective phosphate detection within remarkably low limits of detection of 178 × 10⁻¹²m(17.3 parts per trillion) in buffered samples and stable operation in seawater. This receptor‐based doping strategy, in conjunction with the versatility of EGOFETs for miniaturization and monolithic integration, enables manifold opportunities in diagnostics, healthcare, and environmental monitoring.