Probing Field-Assisted Exciton Dissociation in Y6 via Transient Electro-Absorption Spectroscopy

Chun-Hao Li^1*, Chih-Hsuan Lu¹, Bo-Han Chen¹, Shang-Da Yang¹, Kai Chen², Chun-Jen Shih³

¹Institute of Photonics Technologies, National Tsing Hua University, Hsinchu City, Taiwan
²School of Chemical and Physical Science, Victoria University of Wellington, Wellington, New Zealand
³Organic Electric-ics Research Center and Department of Electronic Engineering, Ming Chi University of Technology, New Taipei City, Taiwan

* Presenter:Chun-Hao Li, email:ljh.ec34@gmail.com

Organic photovoltaic (OPV) materials have attracted significant attention as promising candidates for lightweight and solution-processable solar energy conversion. Among the numerous non-fullerene acceptors developed in recent years, Y6 stands out due to its exceptional power conversion efficiency and favorable optical–electronic properties. However, a long-standing debate persists: can neat Y6 intrinsically generate free charge carriers, or does charge separation necessarily rely on donor–acceptor interfaces?



In this work, we employ transient absorption spectroscopy to probe the excited-state dynamics of neat Y6 films under externally applied electric fields. By systematically varying the bias polarity and excitation conditions, we observe that photoexcitation predominantly creates bound excitons with binding energies exceeding the thermal energy at room temperature. The application of an external electric field induces clear signatures associated with exciton dissociation and free carrier generation, demonstrating that field-assisted separation is essential for charge generation in neat Y6.



Our results provide direct experimental evidence for the field-dependent nature of charge generation in Y6 and offer new insights into the interplay between molecular energetics, exciton binding energy, and external perturbations. These findings not only clarify the intrinsic photophysical behavior of Y6 but also highlight strategies for optimizing next-generation OPVs, including the potential realization of efficient single-component organic solar cells.

Keywords: Organic materials , Y6, Transient absorption spectroscopy