Flexible and Wearable Devices Based on Colloidal Quantum Dots

A significant class of semiconductor nanostructures, colloidal quantum dots (CQDs), which exhibit narrow emission spectrum and tunable emission frequency, are utilized for numerous flexible and wearable applications including state-of-the-art display, biological sensing, showcasing great prospects in physiological measurement, health monitoring, and rehabilitation. Interestingly, synthesizing these semiconductor particles using methods such as hot injection as colloids can directly tune their optical properties and emission wavelengths by controlling their sizes, which greatly contributes to materials production simplicity and scalability. Importantly, from a device perspective, due to the advantages of solution-processed synthesis, and patterning methods such as inkjet printing, CQDs can be combined with soft polymeric substrates, or hierarchical structures in a facile manner, offering extraordinary device flexibility and portability. As optoelectronic devices, CQD can function as photoresistors, phototransistors, or through other mechanisms which convert light between other forms of energy, enabling highly sensitive detection applications. In this Review, synthetic approaches are summarized for CQDs, flexible device fabrication techniques, detection mechanisms, and application scenarios. Furthermore, the challenges associated with these technologies, such as device stability and cost-efficiency are discussed, and present this outlook on the future trends of CQD devices including multi-functional integration, as a constituent component of flexible and wearable devices.