Browsing by Author "Chen, Sheng-Hui"

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Formation and characterization of preferred oriented perovskite thin films on single-crystalline substrates
(2018-06-01)
Chen, Lung-Chien
;
Chen, Cheng-Chiang
;
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.
Multi-band filter design with less total film thickness for short-wave infrared
(2017-01-01)
Yan, Yung-Jhe
;
Chien, I-Pen
;
Chen, Po-Han
;
Chen, Sheng-Hui
;
Tsai, Yi-Chun
A multi-band pass filter array was proposed and designed for short wave infrared applications. The central wavelength of the multi-band pass filters are located about 905 nm, 950 nm, 1055 nm and 1550 nm. In the simulation of an optical interference band pass filter, high spectrum performance (high transmittance ratio between the pass band and stop band) relies on (1) the index gap between the selected high/low-index film materials, with a larger gap correlated to higher performance, and (2) sufficient repeated periods of high/low-index thin-film layers. When determining high and low refractive index materials, spectrum performance was improved by increasing repeated periods. Consequently, the total film thickness increases rapidly. In some cases, a thick total film thickness is difficult to process in practice, especially when incorporating photolithography liftoff. Actually the maximal thickness of the photoresist being able to liftoff will bound the total film thickness of the band pass filter. For the application of the short wave infrared with the wavelength range from 900nm to 1700nm, silicone was chosen as a high refractive index material. Different from other dielectric materials used in the visible range, silicone has a higher absorptance in the visible range opposite to higher transmission in the short wave infrared. In other words, designing band pass filters based on silicone as a high refractive index material film could not obtain a better spectrum performance than conventional high index materials like TiO2 or Ta2O5, but also its material cost would reduce about half compared to the total film thickness with the conventional material TiO2. Through the simulation and several experimental trials, the total film thickness below 4 um was practicable and reasonable. The fabrication of the filters was employed a dual electric gun deposition system with ion assisted deposition after the lithography process. Repeating four times of lithography and deposition process and black matrix coating, the optical device processes were completed.
Unraveling current hysteresis effects in regular-type C-60-CH3NH3PbI3 heterojunction solar cells
(2017-12-07)
Chen, Lung-Chien
;
Lin, Yu-Shiang
;
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.