Novel INFIQ® Lead-Free Infrared Quantum Dot Inks for Photodetection Applications

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Photodetection of infrared (IR) light is used in many industries where the unique properties of sensing and imaging add significant capabilities beyond those of visible light. Current markets include telecommunications, surveillance, spectroscopy, thermal imaging and healthcare, with growing demand in applications for consumer/mobile devices, autonomous vehicles, and novel medical diagnostics.Colloidal quantum dot (CQD)-based IR photodetectors have shown exceptional promise to disrupt incumbent IR technologies combining wavelength tunability, high responsivity and solution processability. The current dominant technology uses lead sulphide (PbS) nanoparticles. Lead (Pb) is restricted hazardous substances under RoHS Directive 2011/65/EU; it is a heavy metal and carries environmental and health concerns. An optimal approach would avoid such compliance issue whilst minimising health and environmental impacts in a product's life cycle, from manufacture to eventual disposal.The PbS QD devices also require a layer-by-layer deposition process involving up to 14 layers. Each layer requires multiple chemical treatment and washing steps, using large volumes of chemicals and solvents that are costly and must be disposed of safely.This project will solve all these problems by developing novel lead-free QD inks and demonstrate their applications in short-wave infrared (SWIR) photodetectors, through a simple one step deposition process. To date, alternative lead-free QD materials have not been synthesised with sufficiently high quality and large scale for optoelectronic device applications. Quantum Science Ltd (QS) has proprietary processes and know-hows to make scalable lead-free SWIR CQDs demonstrating highly efficient conversion of IR light for photodetection. The current challenge is to upscale the material synthesis and provide the QDs in right status enabling simple and low-cost CQD film coating for mass production of SWIR photodetectors.In this project the lead-free CQDs will be synthesised using upscaling method, and surface functionalised with conductive ligands in the same synthesis reactor without pre-purification of the synthesised QD. Different pre-screened novel ligands, eco-friendly solvents and processing conditions will be assessed and QD ink formulations will be optimised and used to deposit films for device fabrication.This project will deliver lead-free CQD inks with leading performance in devices for mass production of high-performance SWIR photodiodes to meet our customers' requirements for the next stage of commercialisation.