Thursday 11 July 2013

solar cell cont.

when the p-type & n-type semiconductors are brought into contact, the magic begins. the crazy electrons at the n-side see the positive holes (p-side) and are fully attracted, they rush towards the holes without a word. however, at the junction between the 2 materials, the electrons and holes attract each other and form a barrier. this barrier make it hard for the electrons to penetrate to the other side. once equilibrium has reached, the barrier acts like a forward diode, making the electrons to move from p-side to n-side but not the other way round.

when a photon from sunlight strike on the surface & move towards the junction, they break apart and the electron is send to the n-side and the hole to p-side, making it more imbalance. now when an external circuit is connected between the n-side and p-side, the resistance is relative low and electrons will tend to flow from n-side to p-side. since current is generated at the opposite direction to electron flow and voltage is produced by the cell electric field (due to p and n-side semiconductor producing an electric field) , power is obtained. (P=I*V)