Si-H Hydrosilane Reducing Agents for Size- and Shape-Controlled InAs Colloidal Quantum Dots.

Abstract

InAs colloidal quantum dots (CQDs) are a promising heavy-metal-free material for infrared optoelectronic devices. However, their synthesis is limited by their reagents: the acutely toxic and difficult to source tris(trimethylsilyl)arsine ((TMS)3As), as well as the strong reducing agents (e.g., Super Hydride). A reducing agent is introduced based on hydrosilanes (Si-H) to address both challenges. A synthesis strategy with this agent is demonstrated, resulting in monodisperse InAs CQDs with a tunable first excitonic peak between 520 and 900nm by hot injection, and between 900 and 1550nm by continuous injection. Furthermore, by avoiding the use of carboxyl group-containing compounds, such as oleic acid or indium acetate, the synthesis minimizes surface oxidation during InAs CQDs formation. The synthesized InAs CQDs are of high optoelectronic quality, with a lower concentration of deep trap states, as evident by the remarkable characteristics of photodetectors fabricated from these CQDs: low dark current (≈150 nAcm-2), external quantum efficiency (32% at 900nm), and a fast photoresponse time (≈4.4 µs). The elimination of (TMS)3As in the synthesis overcomes a key practical barrier for exploiting and exploring the properties of large InAs CQDs in optoelectronic applications.