In-situ regrowth and purification by zone melting of organic single-crystal thin films yielding significantly enhanced optoelectronic properties

Amorphous or polycrystalline films of three organic materials (solvent blue 35 and two porphyrins) have been recrystallized into single-crystal thin films (of micrometer thickness) by a zone-melting technique, in which an electrically heated wire generated a narrow molten zone (0.5-2 mm wide) on the organic layer sandwiched between two pieces of glass or indium-tin oxide-coated glass. When the molten zone was moved slowly (3-120 mu m/min) across the layer from one end of the cell to the other, a single-crystal film was produced after a single pass. After this treatment, the steady-state short-circuit photocurrent was improved by several orders of magnitude.