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Title: Sn-based organic-inorganic hybrid perovskite for high performance photodetectors
Authors: Liu, Chun Ki
Degree: M.Phil.
Issue Date: 2020
Abstract: Organic-inorganic hybrid perovskites (OIHPs) have emerged as potential candidates for next-generation photodetectors (PDs). They have many advantages over the PDs based on traditional materials, such as low-cost fabrication processes, low material consumption, compatible to flexible PD designs and largely tunable optoelectronic properties. However, there are still many issues that need to be addressed for future applications. One of the most important issues is the toxicity in the typical perovskites. Recently, various lead-free perovskites have been successfully synthesised and shows excellent optoelectronic properties. However, the application of these perovskites is still in the starting stage. Considering the great potential for future applications, more investigation in this direction is urgently needed. The contents in this thesis mainly focus on lead-free perovskites and PDs based on them, including three parts. In Part 1, an overview about lead-free perovskites, basics about PDs and PDs based on lead-free perovskites are given. First, the superior properties of lead halide perovskites are reviewed briefly. Then, variety of experimentally realized lead-free perovskites are introduced one by one. Next, the important figures of merits and common device architectures of PDs are discussed. Finally, the recent development of PDs based on various lead perovskites are reviewed. Part 2 presents a high performance PD based on one single layer of lead-free Sn-perovskite. The PD has surprisingly high responsivity and gain of up to 105 A/W and 105. The high performance of the PDs is due to the high quality of the perovskite film, excellent optoelectronic properties as well as the p-doping nature. With the aid of controlled MAPbI3 PD, a simple physical model was proposed to relate the p-doping of Sn-perovskites to the superior device gain. We also showed that the response time can be modulated by changing the film thickness. The device assembled on flexible substrate shows both superior photo-response and bending stability. Part 3 concentrates on another high performance PD by adding one more organic semiconductor layer, Poly(3,4-ethylenedioxythiophene) (PEDOT:PSS), under the perovskite layer as charge transporting layer. The perovskite in the PD acts as absorbing layer. This PD exhibits a responsivity and gain of 106 A/W and 106, respectively. The gain mechanism of this device is mainly due to the photo-gating effect originated from the vertical heterojunction of the perovskite film and PEDOT:PSS , instead of the p-doping nature of the perovskite. This was verified by the low photo-response of the controlled FASnI3- and PEDOT:PSS-only device. Similarly, the device can be fabricated on flexible substrate and demonstrate excellent responsivity and bending stability.
Subjects: Hong Kong Polytechnic University -- Dissertations
Optical detectors
Pages: 110 pages : color illustrations
Appears in Collections:Thesis

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