Role of solvent used to cast P3HT thin films on the performance of ZnO/P3HT hybrid photo detector

Abstract

Abstract The effect of ZnO nanostructured morphology and the role of casting solvent for the active layer of P3HT have been investigated in terms of improved photo response of ZnO/Poly(3-hexylthiophene-2, 5-diyl) (P3HT) hybrid photo detector. Herein, a systematic study has been performed by varying the solvent used for casting of P3HT i.e. Chlorobenzene (CB) and Chloroform (CF). The dark rectification ratio and responsivity of the detector were found to be enhanced by a factor ~25 and ~15, respectively, on changing the solvent from CF to CB. This advancement in the device performance was attributed to the improved morphology of the polymer film which was the result of variation in the casting solvent. Raman spectroscopy and XRD measurements further revealed the better morphology in CB casted thin films of P3HT in terms of improved ordering and crystallinity of the polymer chains. Further, comparing to CF casted thin film, CB casted thin film has provided larger interfacial contact area between polymer and ZnO nanorods, which was confirmed by cross-sectional FESEM measurements of ZnO/P3HT bilayer structure. Large interfacial contact area provides rapid dissociation of excitons which has significantly improved photo response. Furthermore, the enhancement in the photo detector performance parameters were also observed with the variation in ZnO nanorod morphology.