Optical Switching of Hole Transfer in Double-Perovskite/Graphene Heterostructure

Area of Science:

• Materials Science
• Optoelectronics
• Nanotechnology

Background:

• Graphene (Gr)/semiconductor heterostructures are key for optoelectronics due to high charge mobility and light absorption.
• Efficient charge transfer (CT) at the interface is critical for device performance, especially in photodetectors.

Purpose of the Study:

• Investigate ultrafast charge transfer mechanisms in double-perovskite (DP)/graphene heterostructures.
• Determine the role of excitation wavelength on charge transfer direction and efficiency.
• Explore methods to control interfacial charge flow for enhanced photodetector functionality.

Main Methods:

• Fabrication of strongly coupled Cs2AgBiBr6/graphene (DP/Gr) heterostructures.
• Ultrafast optical excitation experiments using varying photon energies (below and above bandgap).
• Analysis of charge transfer dynamics and directionality through experimental evidence.

Main Results:

• Hole transfer is the dominant ultrafast charge transfer mechanism in DP/Gr heterostructures.
• Transfer directionality is tunable: below-bandgap excitation injects holes into DP defect states, while above-bandgap excitation transfers holes from DP to Gr.
• Increasing excitation photon energy enhances CT efficiency in both regimes, highlighting the role of excess energy.

Conclusions:

• Wavelength-dependent hole transfer provides a novel mechanism to control interfacial charge flow in DP/Gr heterojunctions.
• This control enables tuning of the interfacial photogating field, crucial for advanced photodetector design.
• Findings offer a new pathway for optimizing optoelectronic devices based on perovskite/graphene interfaces.