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.This work was supported by the Nano R&D program, Korea Science and Engineering Foundation, South Korean Ministry of Education, Science and Technology (M1080300131008M030031010) and Brain Korea 21. R.S. grateful for the Brain Pool Fellowship and visiting professorship at Hanyang University (South Korea), and to Dr B.A.M. University, Aurangabad, India, for study leave