Browsing by Author "Lin, Yu-Pei"

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Compressive Sensing based Location Estimation using Channel Impulse Response Measurements
(2014)
Lin, Yu-Pei
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Tseng, Po-Hsuan
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Feng, Kai-Ten
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電機工程學系
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Department of Electrical and Computer Engineering
Due to the popularity of location-based services in environment with weak GPS signals, indoor location estimation problem have attracted more and more attention in recent years. Among several distance-related measurements, channel impulse response (CIR) reflects multi-path situation between the transmitter and receiver pair and is suitable to describe the characteristic of different positions. Note that CIR, which can be obtained from the inverse Fourier transform of channel frequency response in broadband wireless networks, is supported in most of the commercial standards. In this paper, a novel compressive sensing based location estimation using CIR measurements (CS-CIR) is proposed as well as fingerprinting algorithm. CIR information is collected from each reference point (RP) to access point (AP) and stored in the database. During the on-line stage, the mobile user measures CIR from the AP and compares measured CIR with those CIR values in the database. Note that user position is close to one of the RPs and user position vector is represented as a sparse vector. By applying compressive sensing theory, user position can be recovered by solving l(1)-minimization problem. Simulation result validate that the CS-CIR outperfiffms the K-nearest neighbour method using CIR measurements and conventional received signal strength based methods.
Control of Crystal Structures and Optical Properties with Hybrid Formamidinium and 2-Hydroxyethylammonium Cations for Mesoscopic Carbon-Electrode Tin-Based Perovskite Solar Cells
(2018-09-01)
Tsai, Cheng-Min
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Lin, Yu-Pei
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Pola, Murali Krishna
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Narra, Sudhakar
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Jokar, Efat
Alcohol-based bifunctional ammonium cations, 2-hydroxyethylammonium (HEA(+)), HO(CH2)(2)NH3+, were introduced into formamidinium (FA(+)) tin-based perovskites (HEA(x)FA(1-x)Snl(3); x = 0-1) to absorb light in carbon-based mesoscopic solar cells. We found that HEAP cations play a key role to control the crystal structures, the lattice structures altered from orthorhombic (x = 0) to rhombohedral (x = 0.2-0.4) with greater symmetry. When x was increased to 0.6-1.0, tin and iodide vacancies were formed to generate 3D-vacant perovskites (HEA(x)FA(1-x)Sn(0.6)I(2.33), x >= 0.6) with a tetragonal structure. Tin-based perovskites in this series were fabricated into mesoporous solar cells using one-step drop-cast (DC), two-step solvent-extraction (SE), and SE + 3% ethyl-enediammonium diiodide (EDAI(2)) as an additive. After optimization of device performance with the SE + 3% EDAI2 approach, the HEA(0.4)FA(0.6)SnI(3) (HEAT = 40%) device gave the best photovoltaic performance with J(sc) = 18.52 mA cm(-2)) V-OC 371 mV, FF = 0.562, and overall efficiency 17 = 3.9% after the device was stored for a period of 340 h.
Formation of Stable Tin Perovskites Co-crystallized with Three Halides for Carbon-Based Mesoscopic Lead-Free Perovskite Solar Cells
(2017-10-23)
Tsai, Cheng-Min
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Mohanta, Nayantara
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Wang, Chi-Yung
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Lin, Yu-Pei
;
Yang, Yaw-Wen
We synthesized and characterized methylammonium (MA) mixed tri-halide tin perovskites (MASnIBr(2-x)Cl(x)) for carbon-based mesoscopic solar cells free of lead and holetransporting layers. Varied SnCl2/SnBr2 ratios yielded tin perovskites with three halides (I, Br, and Cl) co-crystallized inside the tin-perovskite. When the SnCl2 proportion was >= 50% (x >= 1), phase separation occurred to give MAS-nI(3-y)Br(y) and MASnCl(3-z)Br(z) in the stoichiometric proportions of their precursors, confirmed by XRD. A device with MASnIBr(1.8)Cl(0.2) (SnCl2= 10%) showed the best photovoltaic performance: J(SC)= 14.0 mAcm(-2), V-OC= 380 mV, FF= 0.573, and PCE= 3.1%, and long-term stability. Electrochemical impedance spectra (EIS) show superior charge recombination and dielectric relaxation properties for the MASnIBr(1.8)Cl(0.2) cell. Transient PL decays showed the intrinsic problem of tinbased perovskites with average lifetimes less than 100 ps.