Transient Grating Spectroscopy of Photocarrier Dynamics in Semiconducting Polymer Thin Films

TL;DR

This study demonstrates the use of transient grating spectroscopy to simultaneously analyze thermal responses and photocarrier recombination dynamics in organic semiconductor thin films, providing insights into their energy transport and electronic properties.

Contribution

The paper introduces transient grating spectroscopy as a versatile technique for concurrent measurement of thermal and electronic dynamics in organic semiconductors, expanding experimental capabilities.

Findings

Photocarrier recombination occurs on a similar timescale to thermal responses.

Recombination rates align with previous studies.

Technique applicable to various conjugated materials.

Abstract

While charge carrier dynamics and thermal management are both keys to the operational efficiency and stability for energy-related devices, experimental techniques that can simultaneously characterize both properties are still lacking. In this paper, we use laser-induced transient grating (TG) spectroscopy to characterize thin films of the archetypal organic semiconductor regioregular poly(3-hexylthiophene) (P3HT) and its blends with the electron acceptor [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) on glass substrates. While the thermal response is determined to be dominated by the substrates, we show that the recombination dynamics of photocarriers in the organic semiconductor thin films occur on a similar timescale and can be separated from the thermal response. Our measurements indicate that the photocarrier dynamics are determined by multiple recombination processes and our extracted recombination rates are in good agreement with previous reports using other techniques. We further apply TG spectroscopy to characterize another conjugated polymer and a molecular fluorescent material to demonstrate its general applicability. Our study indicates the potential of transient grating spectroscopy to simultaneously characterize thermal transport and photocarrier dynamics in organic optoelectronic devices.