Disclosed is a method to modify the electrical conductivity of an organic and/or molecular material including the steps of providing a reflective or photonic structure and of placing the organic and/or molecular material in or on the structure. The method also includes providing a structure (1) which has an electromagnetic mode which is by design, or can be made by way of adjustment or tuning, resonant with a transition in the organic and/or molecular material (2) and controlling, in particular enhancing, the mobility of the charge carriers, and thus the electrical current, in the organic and/or molecular material (2), by way of strongly coupling the material (2) to the local electromagnetic vacuum field and exploiting the formation of extended macroscopic states in the material.