Inverted CdSe/PbSe Core/Shell Quantum Dots with Electrically Accessible Photocarriers

Heterostructured quantum dots (QDs) based on narrow-bandgap PbSe and wide-bandgap CdSe have been studied for applications in near-infrared light sources, photodetection, and solar energy conversion. A common structural motif is a QD consisting of a PbSe core enclosed in a CdSe shell. However, the CdSe shell complicates extraction of band-edge charge carriers from the QD. Therefore, conventional PbSe/CdSe QDs are not suitable for application in photoelectric devices. Here we report inverted CdSe/PbSe core/shell QDs that overcome this drawback. In these structures, both the electron and hole exhibit a significant degree of shell localization and can therefore be easily extracted from the QD. To create these structures, we employ a thin, atomically controlled wetting layer that homogenizes the CdSe core surface and thus promotes directionally uniform growth of the PbSe shell. The synthesized CdSe/PbSe QD films exhibit good photocarrier transport, making them suitable for application in photoelectric devices.