# Reference Depolarization Values for Polar-Organic Aggregates

## TL;DR

This paper introduces a new model to better estimate depolarization effects in polar-organic aggregates, improving predictions for surface work functions and device design.

## Contribution

The paper proposes a heuristic model extending the point dipole approximation by incorporating molecular size for more accurate depolarization predictions.

## Key findings

- The point dipole model breaks down in highly packed organic aggregates.
- The extended dipole model incorporating molecular size aligns well with DFT and MP2 calculations.
- The new model offers a rapid tool for screening polar organic materials for surface functionalization.

## Abstract

A key aspect in the design of mixed polar-organic layers
and metallic
or semiconducting devices is the dielectric constant of the organic
aggregate, which modulates the surface work function and band alignments.
In simple electrostatic models, a monolayer is treated as an array
of point dipoles whose depolarization depends only on an effective
molecular polarizability. However, the absence of a unified framework
in quantum-chemical computational studies leaves the reliability of
the point dipole model uncertain. In this work, we demonstrate the
breakdown of the point dipole approximation for highly packed aggregates
and propose an alternative heuristic model that relies on a second
molecular parameter: the molecular size. The performance of this approach
is validated through comparison with computational methods based on
Density Functional Theory (DFT) and second-order Møller–Plesset
perturbation theory (MP2) calculations. Our extended dipole model
provides robust estimates of depolarization effects, offering a rapid
prescreening tool for selecting polar organic candidates in surface
functionalization.