Photoinduced Polaron Formation in a Polymerized Electron-Acceptor Semiconductor

Area of Science:

• Materials Science
• Photovoltaics
• Polymer Chemistry

Background:

• Polymerized small molecular acceptors (PSMAs) are crucial for advancing all-polymer solar cells (all-PSCs), with current power conversion efficiencies (PCEs) exceeding 16%.
• Despite their potential, the photophysical properties of PSMAs are less understood compared to polymer donors.
• Understanding PSMA photophysics is essential for further performance enhancements in all-PSC technology.

Purpose of the Study:

• To comprehensively investigate the excited state dynamics of a specific PSMA, PZT810.
• To elucidate the role of excitation energy and intensity on photophysical processes within PSMAs.
• To provide insights into the relaxation dynamics and working mechanisms of PSMAs in all-PSCs.

Main Methods:

• Time-resolved spectroscopic investigations of PZT810 under varying pump intensities and photon energies.
• Analysis of exciton dissociation pathways and polaron generation dynamics.
• Comparative study of neat PSMA films to understand fundamental photophysics.

Main Results:

• Excess excitation energy significantly promotes exciton dissociation into free polarons in neat PSMA films.
• Free polarons cannot be generated directly from polaron pairs in neat acceptor films.
• The photophysical behavior of PSMAs is demonstrably mediated by excitation energy and intensity.

Conclusions:

• This research offers a deeper understanding of relaxation dynamics in PSMAs.
• The findings highlight the critical influence of excitation conditions on PSMA photophysics.
• These insights are valuable for optimizing all-PSC performance and designing novel PSMAs.