# Change in carrier generation on changing source amplitude

#1

Hi,
I would like to know why when I change the amplitude of the source the carrier generation for the solar cell does not change. I tried that with the planar solar cell example . I changed the amplitude of the plane wave source from 1 to 100 but I still got the same generation. Could you please let me know why this happens.

Thanks

#2

FDTD normalizes the results with source power. Changing the source amplitude can be important when the nonorm is selected:
https://kb.lumerical.com/en/ref_sim_obj_cw_normalization.html
Plane wave source power of order 10e-14 Watts

Can you please elaborate on what you want to do and provide the link to the application of interest? If you want to change the amount of applied power, use “scale factor” by editing the imported generation rate object in DEVICE simulations.

#3

Hi @bkhanaliloo,

I would like to know the effect of changing the power on the generation rate.I tried the nonorm mode and I changed the amplitude of the source but I got the same generation again.I understand that there is an option “scale factor” but I would like to see the true generation rate calculated directly with respect to change in power so is there a way to do that ?

Thanks

#4

There are two generation analysis groups:

solar_generation: This analysis group is used in planar silicon solar cell application example:
https://kb.lumerical.com/en/index.html?solar_cells_simple_silicon_planar.html

If you check the analysis group, in line 118:

norma = Psolar/sourceintensity(f_solar); # units of 1/nm

which shows that the results are normalized to solar spectrum which has units of W/m^2/m:
https://kb.lumerical.com/en/index.html?ref_scripts_solar.html

This means that the results are correct for solar spectrum.
https://kb.lumerical.com/en/index.html?solar_cells_methodology.html

CW_generation: There is a “source intensity” in the Edit->Analysis->variables which is:

source intensity = input_power / (x_span*z_span)

https://kb.lumerical.com/en/index.html?pic_photodetectors_vertical_photodetector.html

and in line 130 we have:

norma = %source intensity%/sourceintensity(f); # unitless

This quantity can be modified to change the input intensity and amount of generation rate.

For the solar cell examples, since your device will be illuminate by sun you need to use solar generation. If you want to see how the results will be modified by input intensity, you can add a source intensity parameter similar to cw_generation analysis group and modify the scripts.

Please create a new topic where the case is closed i.e. one open case at a time. We are experiencing a heavy support volume.

Hope this was helpful.

#5

Thanks a lot. That has been very helpful.

#6

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