passed as the voltage is scanned from u2212 1v to 1v or 0v to 2v depending on requirements the recorded data for a standard solution is ohmic in this case the resistance can be learned by taking the gradient of this ohmic line dividing this resistance by the cell constant gives the resistivity the inverse of which is the conductivity the solvents are preferably selected from the group consisting of aromatic hydrocarbons like toluene o m or p xylene trimethyl benzene tetralin anisole alkyl anisole e g isomers of methyl and dimethyl anisole naphthalene and alkyl naphthalene in case a volatile additive is used the solvent should be selected such that it can be evaporated from the coated or printed osc layer together with the additive preferably in the same processing step the processing temperature used for removing the solvent and the volatile additive should be selected such that the osc layer is not damaged preferably the deposition processing temperature is from rt to 135 u00b0 c and more preferably from rt to 80 u00b0 c it has been observed that some solvents like for example o xylene are poor solvents for many ionizable compounds that are used conductive additive however a conductive additive that precipitates from the solution over time can cause problems during coating or printing and is a potential for shorts in the opv cell therefore in a preferred embodiment of the present invention the formulation comprises a first solvent having a good dissolving power for the osc compounds and a second solvent being miscible with the first solvent and having a good dissolving power for the conductive additive hereinafter also referred to as u201c carrier solvent u201d the first solvent is preferably non conductive.