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  • Cost affordable

  • Single-crystal silicon is perhaps the most important technological material of the last few decades—the "silicon era"

  • With a recorded single-junction cell lab efficiency of 26.7%, monocrystalline silicon has the highest confirmed conversion efficiency out of all commercial PV technologies, ahead of poly-Si (22.3%) 

  • The high efficiency is largely attributable to the lack of recombination sites in the single crystal and better absorption of photons due to its black color, as compared to the characteristic blue hue of poly-silicon. Since they are more expensive than their polycrystalline counterparts, mono-Si cells are useful for applications where the main considerations are limitations on weight or available area, such as in spacecraft or satellites powered by solar energy

Solar Panel Specs
  • Watts: 370W

  • Amps: 9.35A

  • Volts: 39.6 VDc

  • Weight: 49.6 lbs

  • Size: 78.7 × 39.1 × 1.38 in

Figure 1 - Canadian Solar CS3U-370MS Silver Mono Solar Panel

AC to DC

One issue with grid connected PV systems is that PV cells produce direct current (DC), whereas power grids use alternating current (AC). Inverters to convert DC to AC comes in handy, and this technology allows buildings/ houses to stay connected to the grid and sell excess energy back to the grid

PN Junction

PV cells, consists of PN Junction whose upper N layer is thin enough- typically 1 micrometer- for light to penetrate to the junction. Photons of sufficient energy can eject individual electrons from the silicon crystal structure, creating electron-hole pairs. If that occurs near the junction, the electric field pushes the positive holes downward, into the P-type material. Electrons, being negative, are pushed in the opposite direction, into the N-type material. Metal contacts on the bottom and top of the cell thus become positively and negatively charged like a positive and negative part of a battery for example.


Several factors determine a PV cells efficiency. The most significant relates to the distribution of wavelengths in the solar spectrum.

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Figure 2 - Distribution of Solar Energy in Spectrum Regions

Semiconductor physics shows that a minimum amount of energy, called the Band-gap energy, is required to eject an electron from the semiconductor crystal structure to create an electron-hole pair. 

Silicon is the essential element in semiconductor electronics, and widely used in solar PV cells. Silicon is the second most rich element on the earth, an element we don’t have to worry about running out of, or need to obtain from exports. 

Silicon has a theoretical maximum PV Cell efficiency of about 33% 


Things to consider
  1. Photons with energies above the band gap give up their excess energy as heat. 

  2. Some Photon created electron hole pairs recombine before the junction electric field has a chance to separate them; their energy ends up being lost as heat.

  3. Some light is reflected off the surface 

  4.      a. Can put on an antireflection coating to trap the light within the cell. Ends up being more expensive and a downside for investment.


Popular Solution

            Multi Junction Solar Cells 

High-efficiency multi junction devices use multiple bandgaps, or junctions, that are tuned to absorb a specific region of the solar spectrum to create solar cells having record efficiencies over 45%. This limiting efficiency, known as the Shockley-Queisser limit, arises from the fact that the open-circuit voltage (Voc) of a solar cell is limited by the bandgap of the absorbing material and that photons with energies below the bandgap are not absorbed. Photons that have energies greater than the bandgap are absorbed, but the energy greater than the bandgap is lost as heat. Multijunction devices use a high-bandgap top cell to absorb high-energy photons while allowing the lower-energy photons to pass through. A material with a slightly lower bandgap is then placed below the high-bandgap junction to absorb photons with slightly less energy (longer wavelengths). Typical Multijunction cells use two or more absorbing junctions, and the theoretical maximum efficiency increases with the number of junctions

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