In this study, AZO films were deposited by RF sputtering technique. Then, the state of residual stress in the AZO films was investigated by using spectroscopic ellipsometry (SE) and XRD methods. Our experiments show that a suitable SE model could provide useful indication about the variation of stress in the as-deposited films. However, there is a disparity in the results of the SE fitting and XRD stress analysis for annealed AZO films. Further investigation is required in order to understand the cause of this contradiction. Despite this disparity, the SE technique enables us to monitor strain relaxation in TCO films with a faster and simpler way compared with other methods.

This paper examines the effects of the thermal storage time and Cu addition on the adhesive strength and microstructure of lead-free Sn-3.0 mass% Ag-1.5 mass% Sb-xCu solder joints. The experimental results show that the adhesive strength of the as-soldered specimens increases with increasing Cu addition and increasing strain rate. Meanwhile, for the aged specimens, the adhesive strength increases with increasing strain rate, but decreases with increasing storage time or with increasing Cu addition beyond 1.0 mass%. The microstructures and fracture morphologies of the solder specimens are analyzed by optical microscopy (OM) and scanning electron microscopy (SEM). The observations reveal that the Cu 6 Sn 5 and Ag 3 Sn particles within the solder microstructure coarsen following high temperature storage and thus reduce the adhesive strength of the solder. Finally, it is found that the prolonged aged specimens with a Cu addition of 0.5 mass% or 1.0 mass% fracture in a combined brittle and ductile failure mode, while those with a Cu addition of 1.5 mass% fail as a result of cleavage after following 200 hours of thermal storage and a strain rate of over 1 s À1 , but otherwise these fracture in a combined brittle and ductile failure mode.

In this study, the quality degradation of multi-crystalline silicon photovoltaic (PV) modules during the aging process was observed by using electroluminescence (EL) technology and IV curve measurements in order to find out the occurring timing of damages on solar cells. The influences of soldering materials and temperatures on the performance of the PV modules were also studied. Experimental data show that, high soldering temperatures which induce high thermal stress can easily lead to the power loss of the PV modules. On PV modules soldered with SnAgPb (SAP) solder, ca. 40% of module damages occurred after 25 cycles during the thermal cycling (TC) test. In contrast, there were 61.5% of damaged SnPb (SP) modules after the 25 TC. Most module damages which are attributed to the crack growth and the floating solder emerged during the soldering and encapsulation processes. In our experiment, the average power degradation of all modules was less than 10%.

To find out the important factors which decisively affect the soldering quality of photovoltaic modules, solar cells were soldered under different conditions (different temperatures, PbSn vs. SnAgCu solder, manual vs. semi-automatic). Experimental results show that the soldering quality of PbSn under 350°C in the semi-automatic soldering process was quite stable while the soldering quality of lead-free solder was generally unacceptable in the manual or semi-automatic process under different temperatures. This result indicates that the soldering process with lead-free solder still needs to be further improved. It was also found that most cracks were formed on the interface between the solder and the silver paste and then expanded outwards.