The main objective of this research work is to decrease work function of any given element or compound or material. To decrease the work function of the given material we have to decrease the bandwidth between conduct band and valance band. Because according to definition of work function, the amount of energy that required the remove the electron from valance band of an atom and it is also called ionization energy. These all energies depend upon the band width that is greater than the band width greater energy required to remove the electron from the surface, and less than the band width and lesser amount of energy required to remove the electron from of materials. In this work we are trying to give an theoretical model or relation, how to decrease the work function of a material by applying external pressure on atoms and doping of the material that has screening or shielding effects. With the help of this model we can increase the efficiency of material used in solar cell that is cell work for all range of frequencies and by construction material bases on this we can increase the efficiency of solar cell or any type of material working solar cell principle.