Browsing by Author "Tseng, Zong-Liang"

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Effect of Washing Solvents on the Properties of Air-Synthesized Perovskite CsPbBr3 Quantum Dots for Quantum Dot-Based Light-Emitting Devices
(2020-01-01)
Chen, Lung-Chien
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Tien, Ching-Ho
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Tseng, Po-Wei
;
Tseng, Zong-Liang
;
Huang, Wei-Lun
In order to improve the stability and cost of perovskite CsPbBr3 and establish a preparation process for quantum dot materials with excellent luminescence properties, CsPbBr3 quantum dots were synthesized by the hot injection method and the ice bath method in air ambient. Then, a proprietary purification system was used to improve the properties of the quantum dots and prepare high-quality perovskite quantum dot films. Optimal material and light characteristics were exhibited with ethyl acetate:hexane as the purification solvent. In the solution form, the photoluminescence wavelength could be maintained at 508 nm with almost no shift compared with other conditions, and the quantum yield could reach 99%; however, superior performance was obtained in the thin-film form, which exhibited little to no shift in the photoluminescence wavelength and, surprisingly, achieved a quantum yield of 91.6% with a narrow PL emission with a full width at half-maximum of 28 nm. In addition, exceptional thin-film uniformity was observed from scanning electron microscopy image analyses. The CsPbBr3 quantum dot light-emitting diode purified with ethyl acetate:hexane demonstrated an open-circuit voltage of 4 V, a maximum luminous brightness of 488 cd m(-2), and a maximum external quantum efficiency of 0.14%.
Formation and characterization of preferred oriented perovskite thin films on single-crystalline substrates
(2018-06-01)
Chen, Lung-Chien
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Chen, Cheng-Chiang
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Chang, Sheng Hsiung
;
Lee, Kuan-Lin
;
Tseng, Zong-Liang
Three single-crystalline (Al2O3, GaN/Al2O3 and InAs) substrates are used to assist the formation of crystallographically preferred oriented CH3NH3PbI3 (MAPbI(3)) thin films. The estimation of the lattice mismatch at the MAPbI(3)/substrate interface and water-droplet contact angle experiments indicate that the formation of a preferred oriented MAPbI(3) thin film is induced by the single-crystalline substrate and is insensitive to the surface wettibility of the substrate. Moreover, the experimental results suggest that the lattice mismatch at the MAPbI(3)/single-crystalline semiconductor interface can strongly influence the photovoltaic performance of tandem solar cells.
Perovskite CsPbBr3 Quantum Dots Prepared Using Discarded Lead-Acid Battery Recycled Waste
(2019-03-02)
Chen, Lung-Chien
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Tien, Ching-Ho
;
Ou, Sin-Liang
;
Lee, Kun-Yi
;
Tian, Jianjun
Perovskite CsPbBr3 quantum dot (CsPbBr3-QD) recovery was performed using lead scrap from lead storage batteries. The perovskite CsPbBr3-QD characteristics were analyzed using different PbO/recycled PbO2 ratios. Scanning electron microscopy (SEM) was used to observe the film surface morphology and cross-section. High-resolution transmission electron microscopy (HRTEM) and X-ray diffraction (XRD) were used to observe the perovskite CsPbBr3-QDs' structural characteristics. A photoluminescence (PL) measurement system was used to analyze the optical properties. The results show that lead scrap from lead-acid batteries as a material for perovskite CsPbBr3-QD production can be successfully synthesized. This saves material and also proves that recycling is valuable. The proposed approach is helpful for future material shortages and materials not easily accessible. Although the efficiency is not very high, this process will be purified using recycled lead in the future to achieve higher quantum yield.
Unraveling current hysteresis effects in regular-type C-60-CH3NH3PbI3 heterojunction solar cells
(2017-12-07)
Chen, Lung-Chien
;
Lin, Yu-Shiang
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Tang, Po-Wen
;
Tai, Chao-Yi
;
Tseng, Zong-Liang
Comprehensive studies were carried out to understand the origin of the current hysteresis effects in highly efficient C-60-CH3NH3PbI3(MAPbI(3)) heterojunction solar cells, using atomic-force microscopy, transmittance spectra, photoluminescence spectra, X-ray diffraction patterns and a femtosecond time-resolved pump-probe technique. The power conversion efficiency (PCE) of C-60-MAPbI(3) solar cells can be increased to 18.23% by eliminating the point (lattice) defects in the MAPbI(3) thin film which is fabricated by using the one-step spin-coating method with toluene washing treatment. The experimental results show that the point defects and surface defects of the MAPbI(3) thin films can be minimized by varying the dropping time of the washing solvent. The point defects (surface defects) can be reduced with an (a) increase (decrease) in the dropping time, resulting in an optimized dropping time for obtaining the defect-minimized MAPbI(3) thin film deposited on top of the C-60 thin film. Consequently, the formation of the defect-minimized MAPbI(3) thin film allows for high-efficiency MAPbI(3) solar cells.