Voltage output of a photodiode (solar cell)

In summary, the voltage output is proportional to cos(α), where α is the angle of incidence of light. However, this relationship is not always reliable due to the varying reflectivity and transmission of a photodiode at different angles of incidence.
  • #1
Smooth
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Hi,
I'm trying to figure out how the angle of incidence will affect the voltage output of a photodiode. The obvious answer that comes to my mind is that the voltage output should be proportional to the cos(α), where α is the angle of incidence of light. However, I couldn't find any formula/article that states this.

Is that true? If so, where can I read about it?

Also, an important thing is that I'm interested in the case when the photodiode is in space – so I can assume that there is no reflected light interfering with the readings. Cause I found some people with experimental data that sort of goes along with my assumption:
http://www.diva-portal.org/smash/get/diva2:858954/FULLTEXT02
https://www.researchgate.net/publication/260532829_Effect_of_Tilt_Angle_Orientation_on_Photovoltaic_Module_Performance
 
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  • #2
A quick search on Google returned 391000 results . The subject is well dealt with just in articles which came up on the first page .

What key words have you been using for your searches ?
 
  • #3
Nidum said:
A quick search on Google returned 391000 results . The subject is well dealt with just in articles which came up on the first page .

What key words have you been using for your searches ?
solar cell voltage angle of incidence
photodiode voltage angle

different variations of these.
I couldn't find anything that would give the relationship between the voltage output and the angle of incidence.
 
  • #4
photodiode angle of incidence
 
  • #5
Most of the time, it is best to use the photodiode at near normal incidence for consistent results. The reason is that there is often a window on them, and the reflectivity/transmission of the window will vary with incident angle, and this is in addition to the ## cos(\alpha) ## factor. The reflective losses can be quite significant at steep angles of incidence and will also be polarization dependent. The same even applies for reflections off the photodiode itself. ## \\ ## I believe the Halliday-Resnick physics text shows ## R_{parallel} ## and ## R_{perpendicular} ## as a function of incident angle ## \theta ## for a typical glass. Both curves have low (and equal) reflectivity values at normal incidence and go to ## R=1.0 ## at 90 degree incidence, with a dip for the ## R_{parallel} ## case with a Brewster angle value of ## R_{parallel}=0 ## for some angle ## \theta_B ## before it rises to ## R=1.0 ## at 90 degrees.
 
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  • #6
Clarification: A solar cell is called a photovoltaic device. A photodiode is reverse biased detector that generates a current when light falls on it. It does not generate voltage on its own.

Solar cells are flat and have the cosine projected area dependence that you mention. Photodiodes are often mounted behind a lens, so behavior could differ.
 
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  • #7
marcusl said:
Clarification: A solar cell is called a photovoltaic device. A photodiode is reverse biased detector that generates a current when light falls on it. It does not generate voltage on its own.

Solar cells are flat and have the cosine projected area dependence that you mention. Photodiodes are often mounted behind a lens, so behavior could differ.
Additional item is that a photodiode is often used with a current-to-voltage amplifier, where the photodiode is operated at zero voltage (they can also be reverse-biased for faster response), but ultimately a voltage is what is observed at the output. A photodiode would generate a voltage in the open circuit state (note: in the current mode with the current-to-voltage amplifier it is essentially short -circuited), but the voltage it generates would be less than linear with light intensity. In the current mode, a photodiode is meanwhile quite linear in its response.
 
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  • #8
marcusl said:
Solar cells are flat and have the cosine projected area dependence that you mention. Photodiodes are often mounted behind a lens, so behavior could differ.

My photodiodes are flat though, so I suppose that they too are proportional to the angle of incidence, right?

And I just wanted to thank everybody for helping me! Thank you!
 
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  • #9
Smooth said:
so I suppose that they too are proportional to the angle of incidence,
You can't be sure of that. You can get the spec of all these devices on line. I suggest you search for it (if it's very important to you). Put in the device number and "PV"; that should give you the info.
 

FAQ: Voltage output of a photodiode (solar cell)

1. What is the voltage output of a photodiode (solar cell)?

The voltage output of a photodiode, also known as a solar cell, varies depending on several factors such as the intensity of light, the surface area of the cell, and the materials used. On average, a single photodiode can produce a voltage output of around 0.5 to 1 volt.

2. How does the intensity of light affect the voltage output of a photodiode?

The intensity of light has a direct impact on the voltage output of a photodiode. As the intensity of light increases, the voltage output also increases. This is because more photons are absorbed by the photodiode, resulting in a higher number of electron-hole pairs being generated and a higher voltage output.

3. Can the voltage output of a photodiode be adjusted?

Yes, the voltage output of a photodiode can be adjusted by changing the surface area of the cell or by using different materials. Increasing the surface area of the photodiode allows for more light to be absorbed, resulting in a higher voltage output. Similarly, using materials with a higher bandgap can also increase the voltage output.

4. What is the maximum voltage output of a photodiode?

The maximum voltage output of a photodiode is limited by the bandgap of the materials used. The highest possible voltage output is the bandgap energy divided by the charge of an electron. For silicon-based photodiodes, this is around 0.7 volts.

5. How is the voltage output of a photodiode measured?

The voltage output of a photodiode can be measured using a voltmeter. The photodiode is connected to the voltmeter in parallel, and the voltage output is recorded. It is important to note that the voltage output may fluctuate depending on the light source and other external factors, so multiple measurements should be taken to get an accurate average value.

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