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

16 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

Bibliographical note

KAUST Repository Item: Exported on 2020-10-01
Acknowledgements: N.B., G.J.M., and M.C. acknowledge the Swiss National Science Foundation (Grant 200020_184819) and the University of Bern for financial support. J.F.M.H and M.R. acknowledge funding from STFC (Grant ST/L006294/1). M.R. acknowledges funding from EPSRC (Grant EP/ L026066/1) and the European Union in FP 7 (Grant 630864). This Letter is based upon work from COST Action StableNextSol MP1307 supported by COST (European Cooperation in Science and Technology), which funded Short Term Scientific Missions (STSMs) of I.R. to TU Dresden and of J.F.M.H. to the group of N.B. I.R. and A.J. acknowledge funding from EPSRC Doctoral Training grant
awards, and A.J. acknowledges a Wolfson-Marriott Scholarship from Wolfson College, Oxford. Furthermore, this publication is partially based upon work supported by the King Abdullah University of Science and Technology (KAUST) Office of Sponsored Research (OSR) under Award No. OSR-2018- CARF/CCF-3079. The GIWAXS data was obtained during experiment nt13183-1 at Diamond Lightsource beamline I07. We thank Dr. Koen Vandewal, Dr. Donato Spoltore (both TU Dresden), Prof. Dieter Neher (University of Potsdam), and Prof. Martijn Kemerink (University of Heidelberg) for fruitful discussions.

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