Wetting-Layer-Assisted Synthesis of Inverted CdSe/PbSe Quantum Dots and their Photophysical and Photo-Electrical Properties

TL;DR

This paper introduces a novel inverted CdSe/PbSe quantum dot synthesis method using a wetting layer, resulting in improved charge carrier extraction and enhanced photophysical and photo-electrical properties for optoelectronic applications.

Contribution

The study presents a new synthetic approach for inverted CdSe/PbSe quantum dots employing a wetting layer, overcoming limitations of traditional structures for photoconversion devices.

Findings

Inverted QDs show efficient photocarrier transport.

Wetting layer promotes uniform shell growth.

Enhanced suitability for photovoltaics and photodetectors.

Abstract

Heterostructured quantum dots (QDs) based on narrow-gap PbSe and wide-gap CdSe have been studied with an eye on their prospective applications in near-infrared (NIR) light sources, photodetectors, and solar cells. The most common structural motif is a spherical QD comprising a PbSe core enclosed into a CdSe shell. However, the potential barrier created by the CdSe shell complicates extraction of band-edge charge carriers from the QD. Therefore, conventional PbSe/CdSe QDs are not suitable for applications in practical photoconversion devices. Here we report inverted CdSe/PbSe core/shell QDs that overcome this drawback. In these structures, both photocarriers (electron and hole) exhibit a significant degree of shell localization and are therefore free to move within the QD solid and be extracted into an external circuit. To create such QDs, we employ a novel synthetic method in which a thin, atomically controlled wetting layer is used to homogenize the surface of the CdSe core and thus promote directionally uniform growth of the PbSe shell. Unlike noninverted QDs, inverted core/shell structures exhibit highly efficient photocarrier transport, making them excellent candidates for applications in practical photoconversion including photovoltaics, photodetection, and photochemistry.