Tuning Out-of-Plane Charge Transport via Spacer-Cation Positional Isomerism in 2D Layered Perovskites

Area of Science:

• Materials Science
• Solid-State Physics
• Photovoltaics

Background:

• Two-dimensional layered perovskites offer improved stability for solar cells.
• Understanding organic spacer chemistry's role in charge transport is crucial.

Purpose of the Study:

• Investigate how position-selective monofluorination of phenethylammonium (PEA) cations affects vertical charge transport.
• Determine the impact of fluorination position on interlayer charge transfer dynamics.

Main Methods:

• Utilized ab initio molecular dynamics, projection-operator diabatization, and semiclassical Marcus theory.
• Examined the effects of ortho, meta, and para fluorination on PEA cations.

Main Results:

• Fluorination position significantly influences interlayer charge transport.
• Meta- and para-fluorinated systems show enhanced charge transfer compared to pristine and ortho-analogues.
• Meta-fluorination optimizes spacer packing and reduces reorganization energy, accelerating charge transport.

Conclusions:

• Positional isomerism is a key design parameter for controlling charge transport in layered optoelectronic materials.
• Findings provide design principles for optimizing charge transport in perovskite photovoltaics.
• Achieved subnanosecond charge transfer rates through strategic fluorination.