Temperature and Angle Dependence

This page describes attempts to determine the effect of temperature and angle on solar cell QE.

Temperature Dependence Measurements

These measurements were performed on solar cell 24 (impedance 3500). A temperature sensor was glued to the acrylic solar cell backing and to the photodiode (see temperature sensor add-on for the relevant circuit - the resistor for the solar cell is 18.09 kOhm and the resistor attached to the photodiode is 17.95 kOhm). These were both hooked up to Keysights, and voltage measurements were taken on the photodiode temperature sensor when current measurements were taken from the photodiode, and voltage measurements were taken on the solar cell temperature sensor when current measurements were taken on the solar cell (these voltage measurements were taken instead of the voltage measurements that used to be taken).

To vary the temperature, a thermostat set to 90 deg F and heating cable were used on the solar cell (insulated with a blanket), turned on for several hours, and then turned off at night. There was no heater on the photodiode. A glass window was used over the solar cell to reduce air currents. You can see the results below, from a dataset taken from 3/31/22 to 4/1/22:

There is a clear temperature dependence that starts at 850 nm and increases as the wavelength increases up to 1.2e-3 QE/degree C at 1050 nm.

Temperature Dependence Theory

These experimental results are qualitatively similar to published measurements and theoretical values of changes in QE in silicon. 

Using https://arxiv.org/abs/1708.02928 and especially the values in https://www.sciencedirect.com/science/article/pii/S0927024808002158, plugged into equation 6 of the paper,

given that these solar cells are 135 um thick, the theoretical dQE/dT from this model is:

See Jupyter notebook: Solar Cell Theoretical QE Temperature Dependence.ipynb

Angle Dependence Measurements

These measurements were also taken with cell 24 on 4/5/2022. Here, the measurements were taken from -25 to 25 degrees, but on inspection, the solar cell was parallel at -10 degrees, so all angle measurements were shifted accordingly, and their absolute values were used for fits.

Note there is also a wavelength dependence here, where shorter wavelengths are more strongly affected (about 3e-4/degree at 450 nm). 

Also, we can compare these measurements to measurements taken on 9/29/2021 with solar cell FX. These measurements are noisier, but consistent with the measurements above.