Photoinduced Electron Transfer for Improved FET Performance Based on the Hybrid Film of an Amphiphilic Perylene Diimide and CdS

A new organic/inorganic PDI/CdS hybrid film is fabricated by using a solution-based Langmuir-Shafer method, inwhich uniformed chrysanthemum-like CdS nanocrystals with an average diameter of ca.120 nm grow in-situ on the Langmuir monolayer of an amphiphilic perylene tetracarboxylic diimide derivative bearing 3,4,5-triethyle-neglycolmonomethyletherphenyl substituents on the imide N atoms and four phenoxy-type substituents in the bay positions of the perylene core (referred to as PDI). Organized film microstructures and slipped co-facialmolecular stacking mode with the "edge-on" conformation are revealed for the PDI in both pure film and hybrid film, with a slightly increased orientation angle with respect to the substrate from 65.4 degrees to 66.8 degrees after incorporation of CdS nanoparticles into the PDI film matrix. Impressively, the electron-transfer from the organic layer to CdS nanocrystals is inferred by both changing the lifetime of photoluminescence emission of PDI in the hybrid film and band structure analysis for PDI and CdS. In particular, upon irradiation of 365 nm UV light, a significantly enhanced electron transport has been obtained in PDI/CdS-based thin film transistors with the carrier mobility up to 1.64 x 10(-3) cm(2)/V.s for electrons, which is two orders of magnitude higher than that (1.91 x 10(-5) cm(2)/V.s) without the irradiation.