Measuring Spatial QE Variation

The setup procedure for measuring the QE variation in a solar cell is a two-part process.  First, the user should mount the solar cell to one of the lab's motorized translation stages (Zaber stages, typically).  The user should wire the cell to an appropriate ammeter from which data can be read onto a computer.

Then, the user must focus a collimated light source onto the front of the solar cell.  This plot should be made as small as possible, which requires some tuning of the focus position. 

Once the user has a point of light focused on the cell's surface, they can begin the measurements.  To make the measurements, the user should move the translation stage in small (0.01 mm) steps, dragging the point of light across the cell's surface.  The zaber translation stage control software is already downloaded on the computers used to do solar cell analyses.  The software is also available open source from the Zaber website: https://www.zaber.com/software/docs/motion-library/ascii/tutorials/install/py/

 Once the data is acquired, it should be stored in a data file showing the stage position in the first column and photocurrent readings in the second.  Here are two sample data files, taken on 05/31/2021 (one for a gen-2 cell, AX, and one for a gen-3 cell, HG):

SC_AX_scanPerpElectrodes_10umPinhole_20210531.txt 

SC_HG_scanPerpElectrodes_10umPinhole_20210531.txt

Then, the user can run the showSCSpatialScans.py analysis code, available on this page of the stubbslab repo: https://github.com/stubbslab/solarCells, to process the acquired data:

$ python showSCSpatialScans.py

Note, the user needs to change the following variables in that .py file to reflect the actual code that they would like to process: 

stems, suffixes, dae_strs, cell_ids, shunt_resistances 

 The results of running this code on the above data files produce this plot: 

The significance of these results are discussed in more detail in our paper: 
Solar Cell Manuscripts