|Title:||Optically-controlled multifunctional electronic devices|
|Subject:||Hong Kong Polytechnic University -- Dissertations|
Embedded Internet devices
Internet of things
|Department:||Department of Applied Physics|
|Pages:||xiii, 133 pages : color illustrations|
|Abstract:||In the era of information explosion, Internet of Things (IoT) has emerged as a technological revolution. With the rapidly increased number of IoT devices, IoT will drive unprecedented volumes and demands for the electronics industry. A multi-functional and highly integrated device can well benefit the IoT system operation and cater for the demands of smart device, such as reducing cost and device occupation area, and lowering energy consumption and electric loss. In this thesis, we design two types of optically-controlled multifunctional electronic devices: (1) multifunctional solar-power supercapacitor by integrating novel perovskite solar cell and electrochromic supercapacitor into one device and (2) hybrid organic-inorganic and transition metal oxide based optoelectronic memories, which both integrate sensing, data storage and processing functions. We first demonstrate multifunctional supercapacitor devices: solar-powered photovoltachromic supercapacitors (PVCSs) by vertically integrating a perovskite solar cell (PSC) with MoO₃/Au/MoO₃ transparent electrode and electrochromic supercapacitor into one device. These PVCSs provide a seamless integration of energy harvesting/storage device, automatic and wide color tunability and enhanced photo-stability of PSCs. The color states of PVCSs not only indicate the amount of energy stored and energy consumed in real time, but also enhance the photo-stability of photovoltaic component by preventing its long-time photo-exposure under fully charged state of PVCSs. This work designs a new type PVCS for multifunctional smart window applications commonly made of glass. Except for the multifunctional and integrated solar-powered supercapacitors, to develop optoelectronic memories integrated with the functions of sensing, data storage and data processing is also desirable for the potential Internet of Things (IoT) application. In this thesis, we demonstrate two types of optoelectronic resistive switching memory integrated with sensing, data storage and processing by adopting hybrid organic-inorganic CH₃NH₃PbI₃-xClx perovskites and MoO₃, respectively. Based on the unusual defect physics and excellent light absorption, the CH₃NH₃PbI₃-xClx memory cell designed in our work exhibits low operation voltage of 0.1 V with the assistance of light illumination, long-term retention property, and multiple resistance states. Its unique optoelectronic characteristics enable to perform logic operation for inputting one electrical pulse and one optical signal, and detect the coincidence of electrical and optical signal as well. This design provides possibilities for smart sensor in IoT application. Except for the non-volatile perovskite optoelectronic memory, we also adopted photochromic material MoO₃ as both light absorption layer and storage medium and designed UV switchable optoelectronic memory. The MoO₃ memory enables both non-volatile and volatile resistive switching behaviors according to different light intensity and light wavelength applied. The co-existence of non-volatile and volatile behaviors enables the implementation of light-stimulated short-term (STP) and long-term plasticity (LTP) for neuromorphic computing, which bridges the gap between sensing and neuromorphic computing and is potential for the design of cognitive artificial eyes.|
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