Hole Transfer Dynamics and Optoelectronic Properties in PCE10:FOIC Blends for Organic Photovoltaics

The development of high-performance organic photovoltaic materials has gained significant attention due to their potential for low-cost, flexible, and lightweight solar energy solutions, including semi-transparent photovoltaics for building-integrated applications.^[1] Central to this effort is the optimization of donor-acceptor blends, where efficient charge transfer and exciton dynamics are critical for enhancing device efficiency.^[2]

Among the promising materials, the blend of PCE10, a polymer donor, and FOIC, a non-fullerene acceptor, has shown considerable potential due to its strong near-infrared absorption and favorable energy level alignment.^[3] In this work, we present a comprehensive investigation into the hole transfer dynamics and optoelectronic properties of a blend material for organic photovoltaic applications. Through a combination of theoretical modeling and experimental analysis, we aim to deepen the understanding of the role of the electronic and excitonic structures in the dynamics that govern the charge separation.

We calculated the energy levels and the absorption spectra by DFT for the individual PCE10 and FOIC molecules as well as their blended configurations. In parallel, we performed extensive experimental investigations, including photoelectron spectroscopy (PES) and femtosecond transient absorption spectroscopy, to explore the photo-physical properties of PCE10, FOIC, and their blend. PES measurements allowed us to estimate the ionization energy and electron affinity of the materials, which are critical for understanding the energy level alignment in the blend. The temporal dynamics of the excitons in the blend were further analyzed to unravel the recombination mechanisms that were dominated by the exciton-exciton annihilation (EEA). By comparing the decay times with different probe energies, we show how the hole transfer processes from acceptor to donor within the blend affect the efficiency of the EEA mechanism. These findings deepen our understanding of the complex interactions between donor and acceptor materials in organic photovoltaic systems, providing valuable insights into the recombination processes and charge transfer mechanisms in organic blends.

[1] Yu et al, Chem. Soc. Rev., 52, 4132 (2023).
[2] Ward et al., Adv. Mater. 27, 2496–2500 (2015).
[3] Liu et al, Nat Commun 13, 5194 (2022).