Effect of Different Wavelengths on Voltage of PV Cells

An experiment was conducted to investigate the impact of various colored filter paper on the energy produced by a photovoltaic cell. The purpose of the research is to verify the effect of the different wavelengths of visible light (red, orange, yellow, green, and blue) on the performance of solar cells, and how this can be used for real-life applications in the improvement of efficiency of solar cells as well as energy production.

How do disparate wavelengths of light affect the voltage composed by photovoltaic (PV) cells?

If the wavelength of the light is protracted, then the voltage produced by the PV cell will decrease, because the energy found in a wave is directly proportional to its frequency and inversely proportional to its wavelength.

Independent variable: Wavelength of light

• Because the voltage produced by the photovoltaic cell depends on the wavelength of the light whether the wavelength is short or long; by knowing the wavelength one would be able to conclude if the voltage will increase or decrease.

Dependent variable: Voltage produced by the photovoltaic cell

• This is due to the fact that the wavelength doesn’t depend on any factor and isn’t affected by any other variable.

Controlled variable: The colorless transparent paper

• Since the colorless transparent paper is the main variable that was compared by the colorful paper used.

Constant variable: Light source (flashlight), the position of the light source, the PV cell, the thickness of the papers used.

The quantum model of light was developed thanks to Einstein's description of the photoelectric effect. Each photon, or light packet, has a unique energy that is determined by its vibration frequency. Whereas, Planck's law states that the energy (E) of a photon is E = hf, where f is the frequency and h is Planck's constant (6.626 1034 joule-second). Despite its particle nature, a photon often has wave properties, and the frequency of any wave is equal to the inverse of its wavelength (which is here denoted by w). When the speed of light is c, f = c/w, and Planck's law is written as E = hc/w. In which, photons collide with the electrons of individual atoms as they hit a conducting substance. If the photons have enough momentum, the electrons in the outermost shells are kicked out. After that, the electrons are free to travel through the material. The incident photons can be completely expelled from the substance depending on their energy. The energy of incident photons is inversely proportional to their wavelength, according to Planck's law. The violet end of the spectrum is dominated by short-wavelength radiation, which contains ultraviolet and gamma rays. Long-wavelength radiation, on the other hand, dominates the red end and contains ultraviolet, microwaves, and radio waves. Therefore, the photoelectric and photovoltaic effects are only generated by light with a short enough wavelength in sunlight. This means that a component of the solar spectrum will be used to produce fuel. It doesn't matter whether the light is bright or dark. It just has to include the solar cell wavelength, at the very least. Since high-energy ultraviolet radiation will pass through clouds, solar cells can work even on cloudy days – and they do.

The Wavelength of a wave refers to the distance over which a wave's shape repeats, from one crest to the next, or one trough to the next. A wave contains energy that is directly proportional to its frequency and inversely proportional to its wavelength. Different colors of light all differ in wavelength, the colors of visible light include:

• White light: white light extends from 400 nm to 750 nm. The white light when passed through a prism gets diffracted into all the other colors of the spectrum.
• Red light: the red light of the visible spectrum has a wavelength of about 650 nm. The best place to see natural red color is at sunrise and sunset when red or orange colors are present. This is because, at sunrise and sunset, the wavelengths associated with red and orange colors are not more properly scattered by the atmosphere than the wavelength of other colors (like blue and purple).
• Yellow light: The yellow light has a wavelength of about 570 nm. Low-pressure sodium lamps, like those used in parking lots, emit a yellow (wavelength 589 nm) light.
• Green light: Green light has a wavelength of about 510 nm. Grass appears green because all of the colors in the visible part of the spectrum are absorbed by the grass except green. The grass reflects green wavelength, therefore the grass appears green.
• The blue light: The blue light which we see has a wavelength of about 475 nm. The atmosphere scatters shorter wavelengths efficiently and hence the wavelength associated with blue colour is scattered more efficiently by the atmosphere. This is the reason why we see the sky to be blue.

• Flashlight
• PV cell
• Stand
• Ammeter/voltage meter
• Double-headed alligator clip wires
• Transparent colored paper:

1. Blue
2. White (transparent)
3. Red
4. Green
5. Yellow
6. Orange

1. Connect the black and red wires to the ammeter and the PV cells.
2. Stabilize the flashlight using a stand at a particular and constant position and distance.
3. Turn on the flashlight and the ammeter after turning off the lights.
4. Place the PV cell under the flashlight.
5. Place a white transparent filter paper between the light and the PV cell.
6. Record the reading of the voltage on the data table.
7. Replace the transparent filter paper with a colored one, and write down your observations.
8. Repeat step 7 with the rest of the filter papers.
9. Make sure to conduct the experiment as a total of 3 trials in order to get more precise and accurate data.

Visible light is most effective for energy generation using PV cells since PV cells are more sensitive to wavelengths within the spectrum. The experiment was conducted on the different colors of the visible light spectrum, each with its own wavelength, to find the voltage they produced in the PV cells. The results were as shown in figure 1, with the colors with seemingly longer wavelengths having produced a smaller amount of energy, and vice versa. Red is the color with the highest wavelength in the visible light spectrum, and it produced the lowest amount of energy. The results point to the fact that the voltage produced increases as the wavelength of a light decreases. This is likely due to the fact that the energy of light is inversely proportional to its wavelength and directly proportional to its frequency.

In short, PV cells are sensitive to light from the entire spectrum as long as the wavelength is above the band-gap of the material used for the cell, but extremely short-wavelength light is wasted. This is one of the factors that affect solar cell efficiency. Another is the thickness of the semiconducting material. If photons have to travel a long way through the material, they lose energy through collisions with other particles and may not have enough energy to dislodge an electron. Whereas after scrutinizing the table, it's evident to us that the strongest color (red) appeared to have the longest wavelength of 625 - 780 nm, with the least voltage ranging from 108 - 110 nm. By which, this seems realistic since red is a non-reflective color absorbing less solar cell material.

The results of the experiment support the hypothesis “If the wavelength of the light is longer, then the voltage produced by the PV cell will decrease because the energy found in a wave is directly proportional to its frequency and inversely proportional to its wavelength.” Red color light generates more electricity than other colors. Contrary to popular belief, longer wavelengths of visible light, the ones with less photon energy, are more efficient with photovoltaic cells than shorter, more energetic wavelengths. The efficiency of solar panels, in general, could be improved by exposure to red light. If a way could be found to eliminate or even reduce the light intensity lost due to tinting, the efficiency of solar panels, primarily, could be improved by exposure to red light.

The aim of the study is to see how various wavelengths of visible light (red, orange, yellow, green, blue, and violet) affect solar cell output and how this can be applied in real-world applications to increase solar cell efficiency and energy production. Since solar cells are very useful in powering space vehicles such as satellites and telescopes. They provide a very economical and reliable way of powering objects which would otherwise need expensive and cumbersome fuel sources, therefore, improving the use of solar cells is a vital aspect for our desired future accomplishments. A factor affecting efficiency is the reflectivity of the solar cell. A certain fraction of incident light bounces off the surface of the cell without encountering an electron. To reduce losses from reflectivity and increase efficiency, solar cell manufacturers usually coat the cells with a nonreflective, light-absorbing material. This is why solar cells are usually black.

Overall, the experiemnt preformed went adequetely prudent in terms of the method and execution. However, it would have been better if the voltage of the flashlight was higher and the amount of the colors were more, yet the number of trials could've been also increased by a bit in order to abolish any chance of error. Moreover, ATL skills are often interconnected. Individual skills and skills clusters frequently overlap and may be relevant to more than one skill category. Therefore, the most suitable skill seems to be research since this topic was fairly new to me so I had conducted detailed inquiry and background research into the topic in order to gain new beneficial knowledge. Alongside, critical thinking as this experiment was moderately complex, thus I had to put in extra effort and effective thinking in order to complete the experiment to the best of my ability.