Gangri Cai

Polyelectrolyte multilayer-assisted fabrication of p-Cu2S/n-CdS heterostructured thin-film phototransistors

We demonstrate meticulous fabrication of p-Cu2S/n-CdS heterojunction thin films using a facile wet-chemical approach. Ion exchange of Cu+ with Cd2+ is a serious problem during preparation of Cu2S/CdS multilayered thin films. This issue was addressed by employing polyelectrolyte multilayers on the CdS surface, which completely prevented CdS corrosion, thereby allowing fabrication of heterostructured Cu2S/CdS films. The formation of polyelectrolyte multilayers is monitored using cyclic voltammetry. The heterostructured films are characterized by structure and morphology. We further employed these films as modified p-channel, p-Cu2S/n-CdS thin-film phototransistors, where n-CdS acts as the electron transporting and hole-blocking layer that extracts and grounds the photogenerated electrons. This device exhibited a significant increase in photocurrent density (>75 times), drift mobility (>87 times), and good linearity without having to apply gate voltage, when compared to its individual component device.

Sequential chemical bath deposition of Cu(2-x)Se/CdS film by suppressing ion-exchange reaction.

Chemical bath deposition is an attractive technique to form single- and multilayered metal oxide/chalcogenide films on electrode surfaces. However, the occurrence of desorption and/or ion-exchange reaction during subsequent chemical bath deposition has so far limited preparation of multilayered metal oxide/chalcogenide films. In this paper, we report a method to prevent desorption and ion-exchange reaction of metal oxide/chalcogenide on electrode surfaces using a polyelectrolyte multilayer during sequential chemical bath deposition. By controlling the ion permeability of the polyelectrolyte multilayer, Cu(2-x)Se film was successfully deposited on the CdS film. The Cu(2-x)Se/CdS film is confirmed by UV-vis absorption spectroscopy, scanning electron microscopy, energy dispersive X-ray analysis, and X-ray powder diffractometer. Furthermore, the Cu(2-x)Se/CdS films were investigated as photoinduced charge transfer devices which showed photocurrents of 0.22 mA/cm(2) under illumination (I = 100 mW/cm(2)).