# Thermal Stability of Organic Semiconductor Thin Film Glasses by Local Changes in Spontaneous Orientation Polarization

## TL;DR

This paper studies how organic semiconductor glasses change when heated, using surface potential changes to track their stability and phase transitions.

## Contribution

The study introduces a method to evaluate thermal stability of organic glasses using local polarization changes during phase transitions.

## Key findings

- Vapor-deposited organic glasses show anisotropic molecular orientation and high stability.
- Surface potential changes track phase transitions above the glass transition temperature.
- Polarization shifts in isotropic liquids help assess thermal stability of organic devices.

## Abstract

Vapor-deposited organic semiconductor glasses exhibit
distinct
molecular anisotropy and exceptional kinetic and thermodynamic stability,
distinguishing them from the inherently isotropic and poorly stable
glasses formed through liquid cooling. In this study, we exploit these
unique properties to examine local changes in surface potential as
the stable glass transitions to a supercooled liquid upon heating
above the glass transition temperature (T
g). Vapor deposited glasses of organic molecules with permanent dipole
moments can generate a measurable surface potential due to their anisotropic
molecular orientation. We use local electrostatic force microscopy
and Kelvin probe force microscopy to provide insights into the dynamics
of the phase transformation occurring above T
g. We demonstrate that changes in polarization upon conversion
to the isotropic liquid serve as an effective proxy for tracking this
transition and highlight their potential for evaluating the thermal
stability of organic devices under diverse thermal conditions.