Movement of cracked silicon solar cells during module temperature changes

Cracks in crystalline silicon solar cells can lead to substantial power loss. While the cells’ metal contacts can initially bridge these cracks and maintain electrical connections, the bridges are damaged by mechanical loads, including those due to temperature changes. We investigated the metallization bridges that form over cracks in encapsulated silicon solar cells. Microscopic characterization showed that the crack in the silicon can immediately propagate through the metal grid, but the grid can maintain electrical contact once the load is removed. We also quantified the movement of the cell fragments separated by a crack as a function of temperature. Cell fragments are free to move diagonally and to rotate, so the change in gap across the crack during a temperature change varies along the length of the crack. In one sample, we showed that a 10 ◦C temperature change, causing a 2 µm increase in the separation of cell fragments, was sufficient to cause a reversible electrical disconnection of metallization bridging a crack

The effect of Zn excess on kesterite solar cells

a b s t r a c t Accuracy in composition control has been one of the top issues for fabricating high-performance kesterite (Cu 2 ZnSn(Se,S) 4 ) solar cells. A detailed understanding of the effect of Zn excess on device performance has not yet been demonstrated. Thus, specific criteria for high-performance devices, in particular discriminating between the effects of Zn-rich features at the front versus the back of the absorber, are desired. In this study, we report that co-evaporated kesterite absorbers can demonstrate high device efficiency despite the presence of large quantities of ZnSe. However, the benign presence of ZnSe is found to be conditional. While large ZnSe grains on the back of the absorbers are not harmful to device performance, the ZnSe grains produced by excess Zn near the end of the deposition degrade the cell efficiency from 8% level to 6% level (without anti-reflection coatings). The other effect related to excess Zn on the front of absorber is the facilitation of breakdown in lower reverse bias. The breakdown indicated here occurs only under the illumination of blue photons, and to our best knowledge has not been reported before. The exact mechanism of the breakdown remains open, but it is demonstrated to be related to the photoconductivity of CdS, and is thus possibly a symptom of lateral defect issues in the absorber, caused by the overdose of Zn. The same type of issue contributing to the breakdown may also be responsible for part of the parasitic loses at the working voltage, and therefore warrants further research

Zn-Se-Cd-S Interlayer Formation at the CdS/Cu₂ZnSnSe₄ Thin-Film Solar Cell Interface

The chemical structure of the CdS/Cu2ZnSnSe4 (CZTSe) interface was studied by a combination of electron and X-ray spectroscopies with varying surface sensitivity. We find the CdS chemical bath deposition causes a "redistribution" of elements in the proximity of the CdS/CZTSe interface. In detail, our data suggest that Zn and Se from the Zn-terminated CZTSe absorber and Cd and S from the buffer layer form a Zn-Se-Cd-S interlayer. We find direct indications for the presence of Cd-S, Cd-Se, and Cd-Se-Zn bonds at the buffer/absorber interface. Thus, we propose the formation of a mixed Cd(S,Se)-(Cd,Zn)Se interlayer. We suggest the underlying chemical mechanism is an ion exchange mediated by the amine complexes present in the chemical bath

Atomic Layer Deposition of Copper (I) Sulfide Using Commercially Produced Precursors

Abstract not Available.</jats:p