Dip-coated colloidal quantum-dot films for high-performance broadband photodetectors

Abstract

Dip coating fabrication is considered as an effective solution processing approach that can be easily extended to scale-up QD film production. In this study, CdSe_xTe_1−x quantum dot (QD) films prepared by a dip coating process are introduced to assemble broadband (UV-NIR) photovoltaic detectors. During the dip coating process, the long organic chain ligands (oleic acid) on the surface of the QDs were replaced with short inorganic ligands (iodide) to facilitate charge transport. Finally, a homogeneous large-area (20 cm²) QD film was obtained. As a result, the QD-based photodetector possessed the fast response speed of <20 ms, the high detectivity of 4.6 × 10¹² Jones, and the broad wavelength response range of 300–850 nm without external bias voltage. The device displayed excellent long-term stability in ex situ tests, exceeding 2000 hours without encapsulation. These results suggest that the dip coating method described herein presents a significant step towards the large-scale preparation and extensive promotion of quantum dot film-based optoelectronic devices.