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

Gareth John Moore, Martina Causa', Josue F Martinez Hardigree, Safakath Karuthedath, Ivan Ramirez, Anna Jungbluth, Frédéric Laquai, Moritz Riede, Natalie Banerji

Research output: Contribution to journalArticlepeer-review

5 Scopus citations

Abstract

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 (
Original languageEnglish (US)
Pages (from-to)5610-5617
Number of pages8
JournalThe Journal of Physical Chemistry Letters
DOIs
StatePublished - Jun 23 2020

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