Abstract
This paper reports on electron-beam-induced current (EBIC) characterization of special multicrystalline Si ingot by dendritic growth under high undercooling. Grain boundaries (GBs), dislocations, and their interaction with carbon related precipitates were investigated. The difference between grains from dendrite and non-dendrite growth was compared. In dendrite grains, parallel twins were frequently found. In non-dendrite grains, irregular GBs of various characters co-existed. Both parallel twins and irregular GBs exhibited dark EBIC contrast at room temperature, indicating the presence of minority carrier recombination centers due to impurity contamination. However, sometimes in non-dendrite grains GBs were visualized with bright EBIC contrast with enhanced collection of charge carriers. The origin of the abnormal bright EBIC contrast was explored and it turned out to be SiC related precipitates, which made GBs conduction channels for electron transport.
Highlights
High-quality multicrystalline Si ingot is beneficial for fabricating high efficiency solar cells
3, could be bright contrast, whilst Grain boundaries (GBs) that stayed far away and intragranular defects, have no contrast. This may have indicated that a GB channel becomes active only when it is connected to the electrode
This paper reported electron-beam-induced current (EBIC) study on mc-Si with dendrite growth
Summary
High-quality multicrystalline (mc) Si ingot is beneficial for fabricating high efficiency solar cells. To decrease the effect of GBs and dislocations, many efforts have been made to control the growth and defect density, such as dendrite Si [10], mono-like Si [11,12], and high-performance (HP) mc-Si [13,14]. Despite the different grain structure, the mono-like Si showed a similar carrier lifetime to that of the HP mc-Si [15] This was probably because of impurity contamination during the melting of raw materials in the initial stage of seed growth. Breitenstein et al [19,20] have done a comprehensive study about current shunts at GBs in mc-Si solar cells They performed EBIC imaging from both the frontside and backside of a p-n junction and discovered GB contrast reversing from dark to bright. The origin of bright EBIC contrast at certain defects will be explored
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