Ultrafast Charge Dynamics in Dilute-Donor versus Highly Intermixed TAPC:C60 Organic Solar Cell Blends

Moore, Gareth John; Causa', Martina; Martinez Hardigree, Josue F.; Karuthedath, Safakath; Ramirez, Ivan R.; Jungbluth, Anna; Laquai, Frédéric; Riede, Moritz K.; Banerji, Natalie (2020). Ultrafast Charge Dynamics in Dilute-Donor versus Highly Intermixed TAPC:C60 Organic Solar Cell Blends. The journal of physical chemistry letters, 11(14), pp. 5610-5617. American Chemical Society 10.1021/acs.jpclett.0c01495

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Elucidating the interplay between film morphology, photophysics, and device performance of bulk heterojunction (BHJ) organic photovoltaics remains challenging. Here, we use the well-defined morphology of vapor-deposited di-[4-(N,N-di-p-tolyl-amino)-phenyl]cyclohexane (TAPC):C60 blends to address charge generation and recombination by transient ultrafast spectroscopy. We gain relevant new insights to the functioning of dilute-donor (5% TAPC) fullerene-based BHJs compared to molecularly intermixed systems (50% TAPC). First, we show that intermolecular charge transfer (CT) excitons in the C60 clusters of dilute BHJs rapidly localize to Frenkel excitons prior to dissociating at the donor:acceptor interface. Thus, both Frenkel and CT excitons generate photocurrent over the entire fullerene absorption range. Second, we selectively monitor interfacial and bulk C60 clusters via their electro-absorption, demonstrating an energetic gradient that assists free charge generation. Third, we identify a fast (< 1 ns) recombination channel, whereby free electrons recombine with trapped holes on isolated TAPC molecules. This can harm the performance of dilute solar cells, unless the electrons are rapidly extracted in efficient devices.

Item Type:

Journal Article (Original Article)

Division/Institute:

08 Faculty of Science > Departement of Chemistry and Biochemistry

UniBE Contributor:

Moore, Gareth John; Causa', Martina and Banerji, Natalie

Subjects:

500 Science > 540 Chemistry

ISSN:

1948-7185

Publisher:

American Chemical Society

Language:

English

Submitter:

Olivier Nicolas Ludovic Bardagot

Date Deposited:

02 Jul 2020 10:23

Last Modified:

30 Sep 2020 12:17

Publisher DOI:

10.1021/acs.jpclett.0c01495

Related URLs:

Additional Information:

Funders:
Swiss National Science Foundation: Type: Project Funding, Grant number: 200020_184819
University of Bern

BORIS DOI:

10.7892/boris.144882

URI:

https://boris.unibe.ch/id/eprint/144882

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