These are the cells in which non reversible redox reaction takes place. That is they can give electrical energy only once at the cost of reaction taking place in them , once the reaction is over , the cells get exhausted and can not be used again. And these cells can never be recharged agin.
The substances whose conductivity lies between 10-⁶ to 10⁴ ohm-¹ . The range lies between conductors and insulators. Types 1. n-type :- These type of semiconductors have excess electrons present in the lattice that are responsible for the conduction. These are formed when the group 14 elements like Silicon are doped with group 15 elements