Browsing by Author "Yu, Ing-Song"

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Achieving highly saturated single-color and high color-rendering-index white light-emitting electrochemical cells by CsPbX3 perovskite color conversion layers
(2018-12-21)
Wang, Cheng-Ming
;
Su, Yong-Ming
;
Shih, Ting-An
;
Chen, Guan-Yu
;
Chen, Yan-Zhi
Solid-state light-emitting electrochemical cells (LECs) have been thought to be applicable for display and lighting due to their advantages such as simple device architecture, low-voltage operation and compatibility with inert cathode metals. Among the emissive materials of LECs, ionic transition metal complexes (iTMCs) exhibit relatively higher emission efficiency but they show relatively broader emission spectra, resulting in lower color saturation for display application. Here, we demonstrated that by integrating perovskite-based color conversion layers (CCLs) with blue iTMC-LECs, highly saturated green, yellow, red and deep-red and high color-rendering-index (CRI) white LECs can be obtained. The Commission Internationale de l'E'clairage (CIE) 1931 coordinates of the highly saturated single-color LECs are almost on the boundary of the National Television System Committee (NTSC) color gamut, showing their potential application in display. By mixing perovskites of different colors at an appropriate ratio in the CCLs, the white LECs show a CRI >90, which is among the highest reported values, and a correlated color temperature of 2649 K. Hence the proposed technique can also be one of the good candidates for lighting applications. In addition, both the highly saturated single-color and white LECs still exhibit efficient emission for display and lighting applications.
Atomic Layer Deposition TiO2 Films and TiO2/SiNx Stacks Applied for Silicon Solar Cells
(2016-08-01)
Yang, Zu-Po
;
Cheng, Hsyi-En
;
Chang, I-Hsuan
;
Yu, Ing-Song
;
光電系統研究所
Titanium oxide (TiO2) films and TiO2/SiNx stacks have potential in surface passivation, anti-reflection coatings and carrier-selective contact layers for crystalline Si solar cells. A Si wafer, deposited with 8-nm-thick TiO2 film by atomic layer deposition, has a surface recombination velocity as low as 14.93 cm/s at the injection level of 1.0 x 1015 cm(-3). However, the performance of silicon surface passivation of the deposited TiO2 film declines as its thickness increases, probably because of the stress effects, phase transformation, atomic hydrogen and thermal stability of amorphous TiO2 films. For the characterization of 66-nm-thick TiO2 film, the results of transmission electron microscopy show that the anatase TiO2 crystallinity forms close to the surface of the Si. Secondary ion mass spectrometry shows the atomic hydrogen at the interface of TiO2 and Si which serves for chemical passivation. The crystal size of anatase TiO2 and the homogeneity of TiO2 film can be deduced by the measurements of Raman spectroscopy and spectroscopic ellipsometry, respectively. For the passivating contacts of solar cells, in addition, a stack composed of 8-nm-thick TiO2 film and a plasma-enhanced chemical-vapor-deposited 72-nm-thick SiNx layer has been investigated. From the results of the measurement of the reflectivity and effective carrier lifetime, TiO2/SiNx stacks on Si wafers perform with low reflectivity and some degree of surface passivation for the Si wafer.
Characterization and density control of GaN nanodots on Si (111) by droplet epitaxy using plasma-assisted molecular beam epitaxy
(2014-12-17)
Yu, Ing-Song
;
Chang, Chun-Pu
;
Yang, Chung-Pei
;
Lin, Chun-Ting
;
Ma, Yuan-Ron
In this report, self-organized GaN nanodots have been grown on Si (111) by droplet epitaxy method, and their density can be controlled from 1.1 x 10(10) to 1.1 x 10(11) cm(-2) by various growth parameters, such as substrate temperatures for Ga droplet formation, the pre-nitridation treatment of Si substrate, the nitridation duration for GaN crystallization, and in situ annealing after GaN formation. Based on the characterization of in situ RHEED, we can observe the surface condition of Si and the formation of GaN nanodots on Si. The surface nitridaiton treatment at 600 degrees C provides a-SiNx layer which makes higher density of GaN nanodots. Crystal GaN nanodots can be observed by the HRTEM. The surface composition of GaN nanodots can be analyzed by SPEM and mu-XPS with a synchrotron x-ray source. We can find GaN nanodots form by droplet epitaxy and then in situ annealing make higher-degree nitridation of GaN nanodots.
Effects of N/Ga flux ratio on GaN films grown on 4H-SiC substrate with 4 degrees miscutting orientation by plasma-assisted molecular beam epitaxy
(2017-07-05)
Susanto, Iwan
;
Tsou, Tsung-Han
;
Yang, Zu-Po
;
Lee, Chao-Yu
;
Li, Hui
High-quality GaN films grown on 4H-SiC (0001) substrate with 4 of miscutting orientation have been done by plasma-assisted molecular beam epitaxy with different N/Ga flux ratio. The effect of N/Ga flux ratio on the surface morphology, chemical composition, structural and optical properties was systematically investigated. The observations of in-situ reflective high-energy electron diffraction demonstrated the special surface of SiC substrate and GaN growth transition from two-to three-dimension depending on N/Ga flux ratio. In the Ga-rich condition for epitaxy, Ga droplets formed and the root mean square value of surface roughness increased by the characterizations of scanning electron microscopy and atomic force microscopy which also related to the formation of the pits on the surface due to the accumulation of excess Ga on the surface. The better growth parameter of GaN films in the work is N/Ga flux ratio of 28 at substrate temperature 700 degrees C. Its surface oxide and charge-compensated surface state associated with defects are minimized from the surface composition analysis of X-ray photoelectron spectroscopy. In the structural characterization of high-resolution X-ray diffraction, the value of full width at half maximum and density of threading dislocation are lower to prove the high-quality structure of GaN film grown at N/Ga flux ratio of 28. Finally, the photoluminescence analysis performed the narrow near-band-edge peak and yellow band, corresponding to the better quality of GaN films. In this report, high-quality GaN films on 4H-SiC (0001) with 4 of miscutting orientation have been demonstrated by the reduction of defect states via the different N/Ga flux ratio. N/Ga flux ratio not only influences the growth mechanism and surface morphology, but also the surface chemical composition, crystal quality and optical properties of GaN compound semiconductors. (C) 2017 Elsevier B.V. All rights reserved.
Effects of substrate and annealing on GaN films grown by plasma-assisted molecular beam epitaxy
(2017-06-25)
Yang, Zu-Po
;
Tsou, Tsung-Han
;
Lee, Chao-Yu
;
Kan, Ken-Yuan
;
Yu, Ing-Song
GaN films were deposited by plasma-assisted molecular beam epitaxy on different substrates, i.e. Si (111), Sapphire (0001) and 4H-SiC (0001) with 4 degrees of miscutting orientation. Due to the lattice mismatch between GaN films and substrates, the substrates profoundly affect the growth mechanism of GaN films on them during the epitaxy. The smooth and complete GaN films can be obtained on 4H-SiC substrates based on the analyses of reflection high energy electron diffraction, scanning electron microscopy and atomic force microscopy. Higher quality of GaN films on 4H-SiC was also confirmed by high resolution X-ray diffraction. Photoluminescence measurements show that the compress stress existed in GaN films grown on sapphire, but tensile stress was observed in the films grown on 4H-SiC and Si. Meanwhile, in-situ annealing treatment of post expitxy can remove Ga droplets on GaN films and decrease the surface roughness and defect density of GaN films; however, thermal decomposition on the surface of GaN films was observed in the characterizations of X-ray photoelectron spectroscopy. (C) 2016 Elsevier B.V. All rights reserved.
Enhancement for Potential-Induced Degradation Resistance of Crystalline Silicon Solar Cells via Anti-Reflection Coating by Industrial PECVD Methods
(2018-12-01)
Chen, Tsung-Cheng
;
Kuo, Ting-Wei
;
Lin, Yu-Ling
;
Ku, Chen-Hao
;
Yang, Zu-Po
The issue of potential-induced degradation (PID) has gained more concerns due to causing the catastrophic failures in photovoltaic (PV) modules. One of the approaches to diminish PID is to modify the anti-reflection coating (ARC) layer upon the front surface of crystalline silicon solar cells. Here, we focus on the modification of ARC films to realize PID-free step-by-step through three delicate experiments. Firstly, the ARC films deposited by direct plasma enhanced chemical vapor deposition (PECVD) and by indirect PECVD were investigated. The results showed that the efficiency degradation of solar cells by indirect PECVD method is up to -33.82%, which is out of the IEC 62804 standard and is significantly more severe than by the direct PECVD method (-0.82%). Next, the performance of PID-resist for the solar cell via indirect PECVD was improved significantly (PID reduced from -31.82% to -2.79%) by a pre-oxidation step, which not only meets the standard but also has higher throughput than direct PECVD. Lastly, we applied a novel PECVD technology, called the pulsed-plasma (PP) PECVD method, to deal with the PID issue. The results of the HF-etching rate test and FTIR measurement indicated the films deposited by PP PECVD have higher potential against PID in consideration of less oxygen content in this film. That demonstrated the film properties were changed by applied a new control of freedom, i.e., PP method. In addition, the 96 h PID result of the integrated PP method was only -2.07%, which was comparable to that of the integrated traditional CF method. In summary, we proposed three effective or potential approaches to eliminate the PID issue, and all approaches satisfied the IEC 62804 standard of less than 5% power loss in PV modules.
GaN Layers on Si (111) from Nanocolumns to Nanorods by Plasma-Assisted Molecular Beam Epitaxy
(2015-10)
Yu, Ing-Song
;
Liang, Wen-Han
;
Yang, Dian-Long
;
Yang, Chung-Pei
;
Chang, Chun-Pu
In this report, the characterization of GaN layers grown on p-type Si (111) substrate by plasma-assisted molecular beam epitaxy was investigated. For different growth temperatures (750 degrees C, 800 degrees C and 850 degrees C) and N/Ga flux ratios (0.26, 0.46 and 0.92), we can find the GaN layers transition from nanocolumns to nanorods structures. During the epitaxy of GaN, nanocolumns in the thin films with poor crystal quality were obtained for the growth parameters of low substrate temperature or Ga-rich condition. However, the growth at high substrate temperature or N-rich condition formed GaN nanorods structure, and was beneficial to the crystallization of GaN layers with preferential orientation (0001). In the end, the possible growth mechanism of GaN nanocolumns and nanorods was discussed in the letter.
GaN Layers on Si (111) from Nanocolumns to Nanorods by Plasma-Assisted Molecular Beam Epitaxy
(2015-10-01)
Yu, Ing-Song
;
Liang, Wen-Han
;
Yang, Dian-Long
;
Yang, Chung-Pei
;
Chang, Chun-Pu
In this report, the characterization of GaN layers grown on p-type Si (111) substrate by plasma-assisted molecular beam epitaxy was investigated. For different growth temperatures (750 degrees C, 800 degrees C and 850 degrees C) and N/Ga flux ratios (0.26, 0.46 and 0.92), we can find the GaN layers transition from nanocolumns to nanorods structures. During the epitaxy of GaN, nanocolumns in the thin films with poor crystal quality were obtained for the growth parameters of low substrate temperature or Ga-rich condition. However, the growth at high substrate temperature or N-rich condition formed GaN nanorods structure, and was beneficial to the crystallization of GaN layers with preferential orientation (0001). In the end, the possible growth mechanism of GaN nanocolumns and nanorods was discussed in the letter.
Single material TiO2 thin film by atomic layer deposition for antireflection and surface passivation applications on p-type c-Si
(2018-09-01)
Chen, Tsung-Cheng
;
Yang, Tsuo-Chuan
;
Cheng, Hsyi-En
;
Yu, Ing-Song
;
Yang, Zu-Po
A thin film deposited on the front surface of solar cell plays an important role in reducing the reflection of incident light and providing surface passivation. Although ultrathin TiO2 films have shown excellent performance of surface passivation, simultaneously serving both functions is hindered by the crystallization issue, which can degrade the passivation quality of TiO2 film, as the film thickness is over certain value (few nanometer only). Here we showed that both functions can be satisfied by single material of titanium oxide film through atomic layer deposition at low temperatures. By varying deposition temperatures from 80 to 200 degrees C, the TiO2 film deposited at 80 degrees C can maintain its amorphous phase up to the thickness of 114 nm. In addition, the optimal thickness for antireflection calculated by OPAL 2 is 61 nm, meaning that amorphous TiO2 film to provide antireflection and surface passivation can be achieved. The passivation quality is verified by minority carrier lifetime measurement using photo-conductance decay method and presented the ultralow surface recombination velocity of 8.7 cm/s. Furthermore, the passivation mechanism is investigated by X-ray diffraction (XRD) and secondary ion mass spectroscopy (SIMS), in which the absence of crystalline issue is confirm and both chemical passivation (due to H termination) and field effect passivation (due to residual Cl atoms) are associated with the improvement of passivation quality. A post deposition anneal is conducted on the TiO2 film deposited at 80 degrees C. The results present that extra thermal budgets can ruin the passivation quality, which is explicated by the TiO2 crystallization as the temperature exceeding 350 degrees C from the XRD measurements, and by the descending of Cl atom (also field effect passivation) as increasing of the annealing temperature from the SIMS measurements. (C) 2018 Elsevier B.V. All rights reserved.
Strongly Enhancing Photocatalytic Activity of TiO2 Thin Films by Multi-Heterojunction Technique
(2018-10-01)
Cheng, Hsyi-En
;
Hung, Chi-Hsiu
;
Yu, Ing-Song
;
Yang, Zu-Po
;
光電系統研究所
The photocatalysts of immobilized TiO(2 )film suffer from high carrier recombination loss when compared to its powder form. Although the TiO2 with rutile-anatase mixed phases has higher carrier separation efficiency than those with pure anatase or rutile phase, the single junction of anatase/rutile cannot avoid the recombination of separated carriers at the interface. In this study, we propose a TiO2/SnO2/Ni multi-heterojunction structure which incorporates both Schottky contact and staggered band alignment to reduce the carrier recombination loss. The low carrier recombination rate of TiO2 film in TiO2/SnO2/Ni multi-heterojunction structure was verified by its low photoluminescence intensity. The faster degradation of methylene blue for TiO2 /SnO2/Ni multi-junctions than for the other fabricated structures, which means that the TiO2 films grown on the SnO2/Ni/Ti coated glass have a much higher photocatalytic activity than those grown on the blank glass, SnO2-coated and Ni/Ti-coated glasses, demonstrated its higher performance of photogenerated carrier separation.
Substrate-insensitive atomic layer deposition of plasmonic titanium nitride films
(2017-03-01)
Yu, Ing-Song
;
Cheng, Hsyi-En
;
Chang, Chun-Chieh
;
Lin, Yan-Wei
;
Chen, Hou-Tong
The plasmonic properties of titanium nitride (TiN) films depend on the type of substrate when using typical deposition methods such as sputtering. Here we show atomic layer deposition (ALD) of TiN films with very weak dependence of plasmonic properties on the substrate, which also suggests the prediction and evaluation of plasmonic performance of TiN nanostructures on arbitrary substrates under a given deposition condition. Our results also observe that substrates with more nitrogen-terminated (N-terminated) surfaces will have significant impact on the deposition rate as well as the film plasmonic properties. We further illustrate that the plasmonic properties of ALD TiN films can be tailored by simply adjusting the deposition and/or post-deposition annealing temperatures. Such characteristics and the capability of conformal coating make ALD TiN films on templates ideal for applications that require the fabrication of complex 3D plasmonic nanostructures. (C) 2017 Optical Society of America
Surface Passivation and Antireflection Behavior of ALD TiO2 on n-Type Silicon for Solar Cells
(2013)
Yu, Ing-Song
;
Wang, Yu-Wun
;
Cheng, Hsyi-En
;
Yang, Zu-Po
;
Lin, Chun-Tin
Atomic layer deposition, a method of excellent step coverage and conformal deposition, was used to deposit TiO2 thin films for the surface passivation and antireflection coating of silicon solar cells. TiO2 thin films deposited at different temperatures (200 degrees C, 300 degrees C, 400 degrees C, and 500 degrees C) on FZ n-type silicon wafers are in the thickness of 66.4nm +/- 1.1 nm and in the form of self-limiting growth. For the properties of surface passivation, Si surface is effectively passivated by the 200 degrees C deposition TiO2 thin film. Its effective minority carrier lifetime, measured by the photoconductance decay method, is improved 133% at the injection level of 1 x 10(15) cm(-3). Depending on different deposition parameters and annealing processes, we can control the crystallinity of TiO2 and find low-temperature TiO2 phase (anatase) better passivation performance than the high-temperature one (rutile), which is consistent with the results of work function measured by Kelvin probe. In addition, TiO2 thin films on polished Si wafer serve as good ARC layers with refractive index between 2.13 and 2.44 at 632.8 nm. Weighted average reflectance at AM1.5G reduces more than half after the deposition of TiO2. Finally, surface passivation and antireflection properties of TiO2 are stable after the cofire process of conventional crystalline Si solar cells.
The influence of 2D MoS2 layers on the growth of GaN films by plasma-assisted molecular beam epitaxy
(2019-12-01)
Susanto, Iwan
;
Tsai, Chi-Yu
;
Fachruddin
;
Rahmiati, Tia
;
Ho, Yen-Ten
In the report, the growth of GaN films on the two-dimension molybdenum disulfide (2D MoS2) and c-sapphire via plasma-assisted molecular beam epitaxy (MBE) was investigated. Two kinds of MoS2 layers were prepared by pulsed laser deposition (PLD) and chemical vapor deposition (CVD) techniques. Three different surface conditions were designed for the growth of GaN films. GaN thin films in the form of polycrystalline were successfully grown on the surface of MoS2 layers. From the surface analysis, CVD technique provided an amorphous and rougher MoS2 surface for the MBE growth. On the contrary, PLD supplied a better in-plane and smoother surface for GaN growth which included more stability of surface chemical composition, higher crystallinity and better near-band-edge emission property. To compare with the growth on c-Sapphire, however, the van der Waals expitaxial growth of single-crystalline GaN films on sp(2) bonded 2D MoS2 is still a challenge. The growth of GaN films on sp(3) bonded c-sapphire still performed the best results in the report. In summary, we demonstrate better growth of GaN thin films on 2D MoS2 surface provided by PLD. The hetetrostructure of 3D GaN on 2D MoS2 semiconductors could be useful in the future applications of electronic and optoelectronic devices.