# Radiation Effects in Electret Organic Thin‐Film Transistors Due to High Flux and High Dose X‐Ray Irradiation

## TL;DR

This paper explores how organic thin-film transistors can be used for high-dose X-ray dosimetry and identifies radiation-induced changes in their materials.

## Contribution

The study introduces an electret-based OTFT for high-dose-rate dosimetry and identifies radiation effects using XPS and NEXAFS.

## Key findings

- OTFTs show excellent linearity and agreement with commercial detectors for depth dose measurements.
- Radiation causes oxidation in pentacene and Fermi level shifts in polystyrene, reducing charge mobility.
- Mobility degradation occurs at high accumulated doses, indicating radiation damage in active materials.

## Abstract

Organic electronic devices offer lightweight, flexible, and low‐cost alternatives to conventional semiconductor technologies, with growing interest in dosimetry applications. An organic thin‐film transistor (OTFT) with a polymer electret is presented for high dose‐rate synchrotron dosimetry. The OTFT operates in accumulated‐dose and real‐time readout modes and demonstrates excellent linearity with various beam filtrations. Device response increases with decreasing energy, and simulations reveal gold contacts as the primary source of energy dependence. Depth dose measurements show good agreement with a commercial detector, validating dosimetric performance. Minimal changes in mobility are observed at clinically relevant doses, but mobility degradation becomes apparent after high accumulated doses, indicating radiation damage in active materials. X‐ray photoelectron spectroscopy (XPS) and near‐edge X‐ray absorption fine structure (NEXAFS) techniques are employed to analyze pristine and irradiated active material films separately and in a combined stack. XPS reveals oxidation in pentacene and a Fermi level shift in polystyrene in irradiated films, both of which likely cause the mobility reduction observed in OTFTs. Valence band and NEXAFS spectra show no evidence of new states in the bandgap. These findings demonstrate the potential of OTFTs as dosimeters for high dose‐rates and clarify how radiation alters the molecular structure and electronic behavior of the device.

Electret‐style organic thin‐film transistors are evaluated for synchrotron X‐ray dosimetry at ultra‐high dose rates, showing promising performance and agreement with standard detectors. XPS and NEXAFS reveal radiation‐induced oxidation and Fermi level shifts in pentacene and polystyrene, correlating with reduced charge carrier mobility and providing insight into radiation degradation mechanisms in organic semiconductors.