High efficiency photodetectors fabricated by electrostatic layer-by-layer self-assembly of CdTe quantum dots

Abstract

We demonstrate high-performance photodetectors from multilayers of CdTe quantum dots (QDs). The QDs are synthesized and dispersed in aqueous solution with either 2-mercaptoethylamine (positively charged) or thioglycolic acid (negatively charged) as capping stabilizers. By electrostatic attraction, the charged QDs are self-assembled layer by layer on an indium tin oxide substrate modified with (3-aminopropyl)triethoxysilane. This process allows control of active layer thickness by self-assembly, and can in principle be applied to a wide range of substrates. The photodetector exhibits high responsivity (0.18A∕W) under 0.1V bias due to extremely short capping ligands of QDs, which have high internal quantum efficiency, and the densely packed multilayer structure.