To describe adequately the general trend of experimental methods of photoconductivity measurements and their details is not a simple issue, as different laboratories have their specific systems which vary considerably. Here we will not refer to the different methods used in preparing photoconductors or to the various methods for making ohmic or rectifying contacts. To make an “adequate” or “proper” contact to photoconductors is not a simple problem and there is not an easy solution. This is because the contact material and contact techniques depend on the semiconductor itself. Moreover, both parameters (material and the techniques for making electrical contacts) depend on the type of majority carriers and very often on the concentration of charge carriers also.