Dye-Sensitized Ternary Copper Chalcogenide Nanocrystals: Optoelectronic Properties, Air Stability and Photosensitivity

TL;DR

This study explores how ligand exchange with an organic pi-system affects the structural, optical, and electrical properties of copper chalcogenide nanocrystals, revealing significant improvements in conductivity and photosensitivity, with implications for optoelectronic applications.

Contribution

It demonstrates the impact of ligand exchange on nanocrystal properties, showing enhanced conductivity and photosensitivity, and provides insights into stability and transport mechanisms in hybrid materials.

Findings

Ligand exchange causes contraction in interparticle distance.

Conductivity increases by eight orders of magnitude in copper-deficient copper sulphide selenide.

High optical responsivities of 200-400 A W-1 are achieved with phthalocyanine-capped nanocrystals.

Abstract

We report on the effect of ligand exchange of copper sulphide selenide as well as copper selenide nanocrystals with the organic pi-system Cobalt beta-tetraaminophthalocyanine and analyse changes in the structural, optical as well as electric properties of thin films of these hybrid materials. A strong ligand interaction with the surface of the nanocrystals is revealed by UV-vis absorption and Raman spectroscopy. Grazing-incidence small-angle X-ray scattering studies show a significant contraction in the interparticle distance upon ligand exchange. For copper-deficient copper selenide, this contraction has a negligible effect on electric transport, while for copper-deficient copper sulphide selenide, the conductivity increases by eight orders of magnitude and results in metal-like temperature-dependent transport. We discuss these differences in the light of varying contributions of electronic vs. ionic transport in the two materials and highlight their effect on the stability of the transport properties under ambient conditions. With photocurrent measurements, we demonstrate high optical responsivities of 200-400 A W-1 for the phthalocyanine-capped copper sulphide selenide and emphasize the beneficial role of the organic pi-system in this respect, which acts as an electronic linker and an optical sensitizer at the same time.