Solar Cell :: essays research papers fc

Solar cellsSolar cells today be loosely made of atomic number 14, unrivaled of the most commonelements on Earth. The crystalline silicon solar cell was one of the firsttypes to be developed and it is unbosom the most common type in use today.They do non pollute the atmosphere and they leave behind no harmful waste matterproducts. Photovoltaic cells work effectively even in cloudy conditions andunlike solar heaters, are more efficient at depleted temperatures. They do theirjob silently and in that location are no touching parts to wear out. It is no wonderthat one marvels on how much(prenominal) a device would function.To understand how a solar cell works, it is required to go back tosome basic atomic concepts. In the simplest dumbfound of the atom, electronsorbit a central nucleus, composed of protons and neutrons. each electroncarries one negative charge and each proton one positive charge. Neutronscarry no charge. Every atom has the same number of electrons as there ar eprotons, so, on the whole, it is electrically neutral. The electrons havediscrete kinetic ability levels, which outgrowth with the orbital radius.When atoms bond together to form a unharmed, the electron competency levels mergeinto forget me drugs. In electrical conductors, these bands are continuous but ininsulators and semiconductors there is an "energy gap", in which noelectron orbits canister exist, between the inner valence band and outerconduction band Book 1. Valence electrons help to bind together the atomsin a solid by orbiting 2 adjacent nucleii, while conduction electrons,being less(prenominal) closely bound to the nucleii, are free to move in reception to anapplied voltage or electric field. The fewer conduction electrons there are,the higher the electrical resistivity of the material.In semiconductors, the materials from which solar sells are made, theenergy gap Eg is fairly small. Because of this, electrons in the valenceband can soft be made to jump to the conduction band by the blastoff ofenergy, either in the form of heat or light Book 4. This explains wherefore thehigh resistivity of semiconductors decreases as the temperature is raisedor the material illuminated. The ardor of valence electrons to theconduction band is best accomplished when the semiconductor is in thecrystalline state, i.e. when the atoms are arranged in a precisegeometrical formation or "lattice".At room temperature and low illumination, thoroughgoing(a) or so-called"intrinsic" semiconductors have a high resistivity. that the resistivity canbe greatly reduced by "doping", i.e. introducing a very small amount ofimpurity, of the order of one in a million atoms. There are 2 kinds of