Solubility dependent trap density in poly (3-hexylthiophene) organic Schottky diodes at room temperature

The performance of organic electronic devices strongly depends on nanoscale structure/macroscopic morphology of organic semiconducting material. In this paper, we have examined the solubility dependent crystallinity and electrical charge transport properties of poly (3-hexylthiophene) (P3HT). We have used three different solvents, toluene (TLN), chloroform (CF) and dichloromethane (DCM) to dissolve the same amount of P3HT. We observed significant change in structure, morphology and optical properties of P3HT in these solvents. We obtained highly crystalline and oriented film morphology of P3HT in ultrasonicated DCM solution. Structure and morphology of films have been studied using grazing incidence X -ray diffraction (GIXD) and atomic force microscopy (AFM). The electrical charge transport properties of the films casted using UN, CF and ultrasonicated DCM have been investigated with Schottky diode configuration ITO/P3HT/Al. The current density - voltage (J-V) characteristics are used for extracting the device parameters. The solubility driven trap density is also calculated by J-V characteristics at room temperature. We observed that highly crystalline P3HT in case of DCM has one order of magnitude less traps than P3HT (CF).