Kuan Jen Chen

Intermetallic Phase on the Interface of Ag-Au-Pd/Al Structure

Three wires, Au, Cu, and Ag-Au-Pd, were bonded on an Al pad, inducing IMC growth by a 155 hr high temperature storage (HTS) so that the electrical resistance was increased and critical fusing current density (CFCD) decreased. Observations of the Ag-Au-Pd wire after HTS (0–1000 hr) indicated that IMC between the Ag-Au-Pd wire and Al Pad was divided into three layers: Ag2Al layers above and below the bonding interface and a polycrystal thin layer above the total IMC. A high percentage of Pd and Au existed in this 200 nm thin layer, and could suppress Al diffusion into the Ag matrix to inhibit IMC growth. After PCT-1000 hr, a noncontinuous structure still remained between the IMC layer and interface, and the main phase of IMC was (Ag, Au, Pd)2Al with a hexagonal structure.

IMPROVEMENT IN THERMAL DEGRADATION OF ZnO PHOTODETECTOR BY EMBEDDING SILVER OXIDE NANOPARTICLES

The degraded performance of annealed ZnO-based photodetector can be improved by embedding an Ag interlayer. The Ag interlay converted to Ag2O during ZnO deposition. After Ag2O nanoparticles formed, the interface between ZnO and Ag2O produced band-bending to redistribute charges and increase the Schottky barrier between the electrical contact and ZnO. The excess Ag interlayer created lattice defects, causing the dark current to increase slightly. The increasing visible PL intensity of annealed ZnO, with the increasing Ag interlayer, clarified the transfer of the photo-generated electron.

Preparation of Cu 2 Sn 3 S 7 thin-film using a three-step bake-sulfurization-sintering process and film characterization

Cu2Sn3S7 (CTS) can be used as the light absorbing layer for thin-film solar cells due to its good optical properties. In this research, the powder, baking, sulfur, and sintering (PBSS) process was used instead of vacuum sputtering or electrochemical preparation to form CTS. During sintering, Cu and Sn powders mixed in stoichiometric ratio were coated to form the thin-film precursor. It was sulfurized in a sulfur atmosphere to form CTS. The CTS film metallurgy mechanism was investigated. After sintering at 500°C, the thin film formed the Cu2Sn3S7 phase and no impurity phase, improving its energy band gap. The interface of CTS film is continuous and the formation of intermetallic compound layer can increase the carrier concentration and mobility. Therefore, PBSS process prepared CTS can potentially be used as a solar cell absorption layer.

Characterizations of Cu/Sn–Zn Solder/Ag Interfaces on Photovoltaic Ribbon for Silicon Solar Cells

Sn-xZn (x = 9, 25, and 50 wt%) alloy solders are applied in photovoltaic (PV) ribbon and connected with silicon solar cells. The interfacial microstructures, series resistance, and bonding strength of Sn-xZn PV modules are investigated. Cu5Zn8 and AgZn3 intermetallic compounds (IMCs) were found at the interfaces. The Zn content in the solder dominates the growth behavior of IMCs at the interface. The thickness of the Cu5Zn8 and AgZn3 IMC layer increased with increasing Zn content in the solder, and thus, the series resistance of the PV module also increased. The growth of IMCs can enhance the interfacial adhesion strength, but excess Zn overconsumes the Ag electrode, reducing the bond strength of the PV module. Applying low-Zn-content Sn- xZn solder to PV ribbon avoids overconsumption of the Ag layer and, thus, decreases the series resistance and internal stress.

Metallurgical mechanism and optical properties of CuSnZnSSe powders using a 2-step sintering process

Cu2SnZn(S + Se)4 is an excellent absorber material for solar cells. This study obtained Cu2SnZn(S + Se)4 powders through solid state reaction by the ball milling and sintering processes from elemental Cu, Zn, Sn, S, and Se without using either polluting chemicals or expensive vacuum facilities. Ratios of S/S + Se in CuSnZnSSe were controlled from 0 to 1. The results showed that the 2-step sintering process (400°C for 12 hrs and then 700°C for 1 hr) was able to stabilize the composition and structure of the CuSnZnSSe powders. The crystallized intensity of the CuSnZnS matrix decreased with increasing the Se content. Raising the Se content restrained the SnS phase and reduced the resistance of the absorber layer. In addition, Raman data confirmed that Se caused a Raman shift in the CuSnZnSSe matrix and enhanced the optical properties of the CuSnZnSSe powders. For the interface of CuSnZnSSe film and Mo substrate, Mo could diffuse into CuSnZnSSe matrix after 200°C annealing. The interface thermal diffusion of CuSnZnSSe/ZnS improved the effects of stack to enhance the stability of structure.

Improvement of charge-discharge characteristics of the Mg-Ni powder electrodes at 55°C

Magnesium-nickel (Mg-Ni) powders are used as the anode materials for secondary lithium (Li) ion batteries. Mg-Ni powders with ratios of 1 : 1 (Mg :Ni) are prepared and their structure and electrochemical behavior at room temperature and 55°C are investigated. The results show that adding Ni powders to Mg powders can reduce the charge-discharge capacities and improve cycling life. In charge-discharge cycle testing at 55°C, the Li ion concentration gradually increased with increasing the duration of electrochemical reactions, indicating that the charge-discharge capacities increase with increment of cycling number. The formation of a solid electrolyte interface (SEI) layer restrains Mg ions from dissolving into the electrolyte and thus improves the charge-discharge capacities at high temperature.