Ultrafast Broadband Charge Collection from Clean Graphene/CH₃NH₃PbI₃ Interface

Area of Science:

• Materials Science
• Optoelectronics
• Photovoltaics

Background:

• Efficient charge collection is crucial for optoelectronic and photovoltaic devices.
• Ultrafast and broadband charge collection are key to improving current and energy conversion efficiency.

Purpose of the Study:

• To demonstrate simultaneous ultrafast and broadband charge collection at a clean graphene/perovskite interface.
• To investigate the charge collection dynamics at this novel interface.

Main Methods:

• Direct growth of perovskite on graphene to ensure a clean interface.
• Tunable two-color pump-probe spectroscopy.
• Time-resolved photoluminescence spectroscopy.
• Time-dependent density functional theory calculations.

Main Results:

• Achieved ultrafast (∼100 fs) broadband charge collection of band-edge photocarriers.
• Demonstrated near-unity current collection efficiency (∼99%).
• Graphene extracted hot carriers in ∼50 fs, exceeding perovskite's intrinsic cooling rates.
• Highlighted graphene's unique Dirac linear band structure for efficient hot carrier extraction.

Conclusions:

• A clean graphene/perovskite interface enables simultaneous ultrafast and broadband charge collection.
• Graphene acts as an ideal charge collection layer due to its properties and Dirac band structure.
• This approach offers potential for high-efficiency optoelectronic and photovoltaic devices, possibly exceeding the Shockley-Queisser limit.