Cu2Se nanoparticles with tunable electronic properties due to a controlled solid-state phase transition driven by...

Area of Science:

• Materials Science
• Nanotechnology
• Solid-State Chemistry

Background:

• Stoichiometric copper(I) selenide (Cu2Se) nanoparticles are synthesized via hot injection.
• Understanding air exposure effects on nanoparticle properties is crucial for device applications.

Purpose of the Study:

• To investigate the impact of air exposure on copper(I) selenide nanoparticle surface composition, crystal structure, and electronic properties.
• To explore the potential of controlled oxidation for tuning nanoparticle conductivity.

Main Methods:

• Hot injection synthesis of Cu2Se nanoparticles.
• Characterization using X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and conductivity measurements.
• Monitoring changes under ambient conditions over time.

Main Results:

• Air exposure induced a transformation from semiconducting to ohmic current-voltage response.
• A 3000-fold increase in conductivity was observed within one week.
• Surface oxidation of Cu(+) and Se(2-) led to a solid-state conversion from monoclinic Cu2Se to cubic Cu1.8Se.
• Facile copper ion conductivity and surface oxidation susceptibility drive this transformation.

Conclusions:

• Controlled air exposure offers a method to tune the electronic properties of Cu2Se nanoparticles.
• The observed solid-state conversion enhances conductivity significantly.
• Cu2Se nanoparticle layers can be utilized as both semiconducting and conducting domains in optoelectronic devices by controlling oxidation.