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Impact of Fullerene on the Photophysics of Ternary Small Molecule Organic Solar Cells
Author(s) -
Karuthedath Safakath,
Firdaus Yuliar,
Liang RuZe,
Gorenflot Julien,
Beaujuge Pierre M.,
Anthopoulos Thomas D.,
Laquai Frédéric
Publication year - 2019
Publication title -
advanced energy materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 10.08
H-Index - 220
eISSN - 1614-6840
pISSN - 1614-6832
DOI - 10.1002/aenm.201901443
Subject(s) - ternary operation , organic solar cell , materials science , fullerene , acceptor , ultrafast laser spectroscopy , chemical physics , spectroscopy , charge carrier , absorption (acoustics) , optoelectronics , photochemistry , chemistry , organic chemistry , polymer , physics , quantum mechanics , computer science , composite material , programming language , condensed matter physics
Ternary organic solar cells (OSCs) are among the best‐performing organic photovoltaic devices to date, largely due to the recent development of nonfullerene acceptors. However, fullerene molecules still play an important role in ternary OSC systems, since, for reasons not well understood, they often improve the device performance, despite their lack of absorption. Here, the photophysics of a prototypical ternary small‐molecule OSC blend composed of the donor DR3, the nonfullerene acceptor ICC6, and the fullerene derivative PC 71 BM is studied by ultrafast spectroscopy. Surprisingly, it is found that after excitation of PC 71 BM, ultrafast singlet energy transfer to ICC6 competes efficiently with charge transfer. Subsequently, singlets on ICC6 undergo hole transfer to DR3, resulting in free charge generation. Interestingly, PC 71 BM improves indirectly the electron mobility of the ternary blend, while electrons reside predominantly in ICC6 domains as indicated by fast spectroscopy. The improved mobility facilitates charge carrier extraction, in turn leading to higher device efficiencies of the ternary compared to binary solar cells. Using the (photo)physical parameters obtained from (transient) spectroscopy and charge transport measurements, the device's current–voltage characteristics are simulated and it is demonstrated that the parameters accurately reproduce the experimentally measured device performance.