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Title: Hybrid devices based on graphene and related materials for wearable (opto)electronics
Author: Akhavan, Shahab
ISNI:       0000 0004 9354 1008
Awarding Body: University of Cambridge
Current Institution: University of Cambridge
Date of Award: 2020
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It was as far back as 30,000 years ago that human beings began to wear clothing made from woven fibers. Yet, in the last decades an acceleration in textile technology has seen unprecedented levels of innovation in power loom and spinning frame techniques. With the current competitive global ingenuity in nanoscience and nanotechnology and its implication in textile industry, wearable electronics seems to be the next promising trend in this giant market (25.19 billion US dollars by 2020). Part of this revolution includes the integration of electronics and textiles, which has dramatically cross fertilized the technology and design worlds. However, the use of rigid technologies hindered the viability of the wearable. This dissertation focuses on exploiting graphene and related materials in order to develop novel hybrid device concepts with various functionality and amenability. Here, I propose an on-demand, scalable and cost-effective fully inkjet lithography technique to make sensitive (~337 A/W), broadband (visible till 2.7 μm) and fast response time (~50 ms) hybrid photodetectors (PDs) at 1 V, which is the highest reported performance for PDs among liquid phases exfoliated based PDs. Furthermore, I successfully exploit this technique to fabricate flexible and washable PDs on fabrics operating at only 1 V. Additionally, I present the design and fabrication of conductive fibers via controlled rolling of single layer graphene around individual fibers to construct state-of-the-art all-fiber gate-tunable PDs. Fiber-based PDs exhibit broad spectral photodetection from visible to near infrared (870 nm), fast temporal response time (~5 ms) and high external responsivity (~22,000 A/W) at only 1 V. The devices endure against rigorous standard mechanical and washing tests. I then utilize the same platform to fabricate wearable fiber-based gas sensors for detection of toxic gas molecules. Finally, I demonstrate the novel mesoscopic fabrication method, suitable for graphene and flexible-based solar cells via transferring pre-sintered mesoscopic TiO2 structure. I believe that these findings are not only scientifically intriguing, but also technologically important, the implications of which could see large scale implementation in the next generation of wearable electronics.
Supervisor: Ferrari, Andrea C. Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
Keywords: Wearable ; Flexible ; Photodetectors ; Gas sensors ; Solar cells ; Graphene ; Layered materials ; Perovskite