SPACE-CHARGE-LIMITED CURRENTS DUE TO LARGE POLARONS

A model of charge injection from Ohmic contacts in disordered organic materials is presented, where the charge carriers are large (or small) polarons. We find that the space-charge-limited current is exponentia lly sensitive td the size of the molecules and the width of the polaro n. For large molecules, we recover, at high fields, the usual Fowler-N ordheim-like dependence observed in many current-voltage characteristi cs of polymer light-emitting diodes.