Wei-Ting Ho

Surface passivation of Cu(In,Ga)Se2 using atomic layer deposited Al2O3

With Al2O3 passivation on the surface of Cu(In,Ga)Se2, the integrated photoluminescence intensity can achieve two orders of magnitude enhancement due to the reduction of surface recombination velocity. The photoluminescence intensity increases with increasing Al2O3 thickness from 5 nm to 50 nm. The capacitance-voltage measurement indicates negative fixed charges in the film. Based on the first principles calculations, the deposition of Al2O3 can only reduce about 35% of interface defect density as compared to the unpassivated Cu(In,Ga)Se2. Therefore, the passivation effect is mainly caused by field effect where the surface carrier concentration is reduced by Coulomb repulsion.

Characterization of IrO2 thin films by Raman spectroscopy

Abstract Raman scattering has been used as a technique for characterization of the sputtered IrO 2 thin films (SIROF) deposited on different substrates under various conditions. Compared with the spectrum of single crystal IrO 2 , red shift and broadening of the linewidth of the Raman peaks of SIROF are observed. X-ray diffraction measurements of SIROF were also carried out to assist the identification of the factor that influences the linewidth broadening of the Raman features. The results indicate that amorphous–crystalline transition for IrO 2 phase can be achieved at substrate temperature of 200–300 °C. The line-shape and position of the Raman features vary for films deposited on different substrates under the same conditions. These differences can be due to the existence of stress between IrO 2 and the substrates.

Enhanced corneal wound healing with hyaluronic acid and high‐potassium artificial tears

The aim of this study was to investigate the therapeutic role of preservative‐free artificial tears containing hyaluronic acid and high potassium ion concentration (HA/high‐K artificial tears) on mechanically scraped or alkali‐induced corneal epithelial defects in rats.

Ion implanted boron emitter N-silicon solar cells with wet oxide passivation

An ion implanted boron emitter silicon solar cell is demonstrated. By using appropriate annealing condition, the implanted dopants and damage introduced by the implantation can be activated and repaired, respectively. Both the rapid thermal annealing (RTA) and furnace annealing were investigated within this work. For the surface passivation and the antireflection coating, the wet oxide (SiO2) was grown during the furnace annealing step. Since the wet oxidation process has about one order of magnitude faster than the dry oxidation process, it could be a suitable technology for industrial silicon solar cell processing. The rapid thermal annealing with various temperatures and annealing time were also investigated. The open-circuit voltage increased with increasing the temperature and time of the RTA process. The planar p+nn+ solar cell with wet oxide passivaiton achieves the Voc of 0.631 V and the efficiency of 15.43%.

The investigation of optimal Si-SiGe hetero-structure thin-film solar cell with theoretical calculation and quantitative analysis

The device performance such as short circuit current density (Jsc), open-circuit voltage (Voc), fill factor (FF), and efficiency of solar cells on the multi-crystalline SiGe on the Si with different Ge concentration are compared and investigated in this work. The average Ge concentration was systematically changed in the range from 0% to 30%. The appropriate addition of Ge in crystal Si is the effective way to increase the short circuit current density without affecting the open-circuit voltage, due to the modulation of the material energy band-gap. The band-gap of the SiGe can be extracted by Electron-Hole Plasma (EHP) model at different temperatures. With the optimization of Ge concentration and clean process condition, the overall efficiency of a Si0.9Ge0.1 based solar cell is found to be improved about ∼4% than the control mc-Si solar cell. Moreover, the SiGe based solar cell has also been observed that it has less operated temperature sensitivity than Si solar cell for the real application. The theoretical calculation and simulation work help us to understand and engineer the high-efficiency SiGe solar cell qualitatively.

In Vitro and In Vivo Models to Study Corneal Endothelial-mesenchymal Transition

Corneal endothelial cells (CECs) play a crucial role in maintaining corneal clarity through active pumping. A reduced CEC count may lead to corneal edema and diminished visual acuity. However, human CECs are prone to compromised proliferative potential. Furthermore, stimulation of cell growth is often complicated by gradual endothelial-mesenchymal transition (EnMT). Therefore, understanding the mechanism of EnMT is necessary for facilitating the regeneration of CECs with competent function. In this study, we prepared a primary culture of bovine CECs by peeling the CECs with Descemets membrane from the corneal button and demonstrated that bovine CECs exhibited the EnMT process, including phenotypic change, nuclear translocation of β-catenin, and EMT regulators snail and slug, in the in vitro culture. Furthermore, we used a rat corneal endothelium cryoinjury model to demonstrate the EnMT process in vivo. Collectively, the in vitro primary culture of bovine CECs and in vivo rat corneal endothelium cryoinjury models offers useful platforms for investigating the mechanism of EnMT.

Thermal oxide, Al 2 O 3 and amorphous-Si passivation layers on silicon

The effective passivation needs (1) higher bandgap than Si with type 1 alignment, (2) low interface density at the interface between passivation layer and Si, and (3) ionized charges for field effect passivation. The thermal oxide (SiO2) with low interface defect density seems most effective but requires high growth temperature (900 °C). Al2O3 with trapped negative fixed charges can serve as the field effect passivation. Moreover, doped amorphous Si can also have the field effect passivation with the controlled ionized charge density. The effective life time is measured by quasi-steady-state photoconductance (QSSPC). Photoluminescence (PL) measurement is consistent with QSSPC, and can probe a local area with mapping ability on large samples. The dependence of PL intensity on surface recombination velocity is theoretically studied. The passivation of a-Si becomes less effective after crystallization at high temperature annealing, indicating the larger bandgap is necessary.