PV Gap

Alfredo Said:

How do Solar cells work?

We Answered:

you need to knowledge of photoelectric effect to understand this question.

First of all, in photoelectric effect, light are consider as particle. It is the photons. photon is a package of light carrying energy.

the energy is given by the formula,

E = hf E is energy, h is plank constant, f is frequency of the light

when the photon incident on the surface of a conductor, it will transfer its energy under a few condition,

1. the frequency of the light must be higher than the threshold frequency of the surface for electrons to be liberated from the surface.
2. each photon will give up all its energy to a single electron only.
3. photon will either give all its energy or not at all.
4. the excess energy other than the energy supply to release the electron will be the kinetic energy of the electron.

when electrons are liberated from the surface, charge carriers are present and therefore current can be induced.

Edna Said:

how do most solar cells work?

We Answered:

The most common form of solar cells which are the ones commonly seen on our calculators and watches are called photovoltaic cells, also known as modules. A module, when you come across the term, refers to a group of cells connected and grouped into a single frame.

PV cells, comprised of materials called semiconductors like silicon, fulfill their function by converting sunlight directly into an electrical supply. When the light from the sun contacts the cell part of the light, it is absorbed by the silicon or other semiconductor material. The light absorbed in this way is transported to the semiconductor and the energy produced frees trapped electrons, thereby enabling them to move around freely from layer to layer of the cell. The energy produced by this produces a current. In order to draw off this electrical current to facilitate its external use, metal contacts are positioned on the top and bottom of the photovoltaic cell. The current along with the voltage of the cell is what determine the wattage (or power) that the cell is capable of producing.

Silicon is the most often used material for solar cells as it has many very particular chemical properties, especially when it is in a crystalline state. Basically, silicon atoms have 14 electrons arranged into three separate shells, with the first two shells closest to the middle being totally full. The outer shell is only half full, however, and the atom will continually look to fill up this last shell, with the electrons constantly seeking out its neighboring silicon atoms in order to do so. We therefore end up with effectively each atom ‘holding hands’ with its neighbor – and in the case of the structure of crystalline silicon every atom having four hands joined to four neighbors, a structure that is vital to a photovoltaic cell. In crystalline silicon the electrons are locked into the structure in the way previously described, which makes it an effectively conductor of electricity. Conversely, pure silicon would make a very poor conductor of electricity due to the fact that its electrons are not at liberty to move freely about in contrast to crystalline silicon or other excellent conductors like copper.

The adding of an impurity such as phosphorous is known as ‘doping’, and the silicon that ensues as a result of this doping with phosphorous is known as N-type ( ‘N’ meaning negative) due to the sheer number of free electrons that ensue. This type of silicon is a far more efficient conductor than pure silicon. This accounts for one part of the solar cell. The remaining part of the solar cell is doped with boron, which becomes a P-type (positive) silicon as it has merely three electrons in its outer cell rather than four. These positive type silicons have free holes which are basically a lack of electrons. As a result, they carry a positive charge and can move around also. When the positive and negative silicon types are combined, things start to happen.

Every photovoltaic cell has a minimum of one electric field, without which the cell would be unable to function. The electrical field is able to form once the positive and negative silicon types combine. At this point all of the free electrons in the negative side, which have been seeking holes to fall into, rush to fill all of the free holes on the positive side. Eventually this balances and a barrier forms between the remaining N and P electrons, and an electric field forms. The field allows electrons to flow from side P to side N, but not vice versa. When the light from the sun hits the panel, this energy frees hole pairs. We then get a current as a result of electron flow, and voltage from the cells’ electric field. Our power, in the form of electricity produced by the cell, is the product of these two things.

Terrence Said:

how do solar cells work?

We Answered:

The solar cell is made of silicon.

Photons in sunlight hit the solar panel and are absorbed by semiconducting materials, such as silicon.

Electrons (negatively charged) are knocked loose from their atoms, allowing them to flow through the material to produce electricity.