How Can Solar Cell Work to Generate Electricity ?

As we know that solar cell is a semiconductor material that converts light to electricity, this semi conductor material may be silicon or gallium or cadmium telluride but the crystalline silicon solar cell is the most commonly used to generate electricity representing 95 % of the market share.

How solar cells work?

Regarding crystalline silicon cell, the silicon atom has 4 bonding electrons at the outer shell and all silicon atoms is connecting to each other by sharing electrons to complete the outer shell for each cell to 8 electrons and hence the result is silicon lattice.

To generate the solar cell we introduce impurities (doping atoms) into this silicon lattice to form to type of crystalline silicon:

Type one called : N- type silicon : impurities are phosphorus atoms with (5) electrons in the outer shell so we have one electron more for each connection between one silicon cell and one phosphorus cell so at N – type crystalline silicon we have abundant of negative electrons.

Type two called : P- type silicon: impurities are boron atoms with (3) electrons in the outer shell so we have one electron less (hole) for each connection between one silicon cell and one boron cell so at P – type crystalline silicon we have abundant of positive holes .

If we bring p-type silicon layer together with n-type silicon layer a p-n junction is formed, at this junction the abundant electrons and abundant holes will start to diffuse in opposite directions to each other but fortunately some positive charge atoms remain at n-type layer (at transition region) and some negative charge atoms remain at p-type layer (at transition region), this create a region known as space charge region with an electric field that opposed to the movement of the transition and that result in stopping the diffusion of holes and electrons.

If the solar cell two contacts are externally connected to each other by an outer electrical wire the electrons will flow in wire generating electrical current in the condition that it will be enough energy to motivate electrons.

Now if the solar cell (p-n semiconductor) is exposed to the light (input energy) photons and electrons diffusion will occur and the space region will formed and hence a voltage will present on the solar cell contacts and if the electrical circuit is closed , the current will flow…this process as whole is called photovoltaic which mean converting sun light to electricity.