PbS Quantum Dots Ink with Months‐Long Shelf‐Lifetime Enabling Scalable and Efficient Short‐Wavelength Infrared Photodetectors

Abstract

The phase‐transfer ligand exchange of PbS quantum dots (QDs) has substantially simplified device fabrication giving hope for future industrial exploitation. However, this technique when applied to QDs of large size (> 4 nm) gives rise to inks with poor colloidal stability, thus hindering the development of QDs photodetectors in short‐wavelength infrared range (∼1000‐3000 nm). Here, we demonstrate that methylammonium lead iodide ligands can provide sufficient passivation of PbS QDs of size up to 6.7 nm, enabling inks with a minimum of ten‐week shelf‐life time, as proven by optical absorption and solution‐small angle X‐ray scattering. Furthermore, the maximum linear electron mobility of 4.5 × 10−2 cm2 V−1 s−1 was measured in field‐effect transistors fabricated with fresh inks, while transistors fabricated with the same solution after ten‐week storage retained 74% of the average starting electron mobility, demonstrating the outstanding quality both of the fresh and aged inks. Finally, photodetectors fabricated via blade‐coating exhibited 76% external quantum efficiency at 1300 nm and 1.8 × 1012 Jones specific detectivity, values comparable with devices fabricated using ink with lower stability and wasteful methods such as spin‐coating.This article is protected by copyright. All rights reserved

Suppressing Charge Extraction Loss in Quantum Dot Infrared Photovoltaics by Optimizing the Charge Transport Layer

“…7 In order to achieve the effective absorption of IR photons with energy <1.1 eV, the diameters of PbS QDs are required to be larger than 4 nm, resulting in more exposure of {100} facets on the QDs surface. 8 Thus, much research focus is currently on the surface passivation of QDs in the PbS based IR solar cells. 9,10 However, the n-type electron transport layer (ETL), used for constructing depletion heterojunctions with the p-type QD photoactive layer, plays an equally important role to the other functional layers in the QD IRSCs.…”