Abstract
Herein, a method to quantify the amount of reduction in the internal quantum efficiency (IQE) of multicrystalline silicon solar cells that can be attributed to grain boundaries is presented. By correlating the IQE maps obtained via light beam induced current (LBIC) topography with optical images of Secco‐etched samples, the distribution of IQE values at the positions of grain boundaries can be compared with the distribution of IQE values for all other positions where other defects may exist. The segmentation of IQE at 826 nm maps of the samples shows grain boundaries to be more detrimental compared with the combined effects of all other defects that may exist in other regions of the cell. The grain boundaries reduce the average IQE by up to 4.07% absolute for the cell from the bottom of the ingot.
Highlights
To quantify the collective impact of grain boundaries on the IQE, we need to use a hypothetical average IQE that would serve as a reference value for comparison
A method to quantify the collective impact of grain boundaries on the IQE of Multicrystalline silicon (mc-Si) solar cells has been presented in this work
In comparison with the combined effect of all other crystal defects that may be present at positions of at least 200 μm away from detected grain boundaries, grain boundaries proved to be more detrimental to the IQE at 826 nm in our samples
Summary
Standard aluminum back surface field (Al-BSF) solar cells were fabricated from the bottom, middle, and top ingot positions of a high-performance multicrystalline silicon (HP mc-Si) brick. IQE maps at 826 nm wavelength were obtained using a custombuilt LBIC system.[23] The measurements were conducted at a spatial resolution of 50 μm with incident laser power of about 1.8 μW. Some regions containing structures that could be identified in an etched wafer were mapped at a resolution of 12.5 μm. These maps will aid in correlating the positions of the pixels of the IQE maps with those of the microscope images of the etched samples. Reflection maps, obtained using LBIC, were used to identify the positions of the contact fingers and busbars. Pixels in the IQE maps where the total reflection exceeded 8% were excluded from the analysis
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