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Absence of Mixed Phase in Organic Photovoltaic Active Layers Facilitates Use of Green Solvent Processing

Journal Article · · Journal of Physical Chemistry. C
 [1];  [2];  [3];  [4];  [4];  [4];  [3];  [1]
  1. SLAC National Accelerator Lab., Menlo Park, CA (United States)
  2. SLAC National Accelerator Lab., Menlo Park, CA (United States); Stanford Univ., CA (United States). Electrical Engineering Dept.
  3. Univ. of California, Santa Barbara, CA (United States). Dept. of Materials and Chemistry & Biochemistry
  4. Georgia Inst. of Technology, Atlanta, GA (United States). School of Chemistry and Biochemistry. Center for Organic Photonics and Electronics
+ Show Author Affiliations
In this paper, we examine the morphology of a donor molecule:fullerene organic photovoltaic (OPV) active layer, processed from the “green solvent” 2-methyl-THF (m-THF), as well as the conformation of the two OPV constituent components in the casting solution. We observe that the small molecule (X2) has a weak association with itself in chloroform solvent, whereas it does not self-associate in m-THF. Despite this difference, the morphologies of the final processed films are extraordinarily similar: there is negligible molecularly mixed phase in the layer, and the domain sizes of the pure X2 and pure fullerene are 15–20 nm. We attribute this similarity between the final films to the strong aggregation behavior of X2 upon drying; changes in solvent or solvent additive have therefore only a minor effect on the final bulk heterojunction morphology. This contrasts with the majority of other OPV molecular donor semiconductor systems, which need careful tuning of solvent and/or solvent additive to achieve the optimal morphology and photovoltaic performance. Finally, we argue that the absence of a mixed phase is a result of the strong self-aggregation behavior of X2 and a key property of this material combination that makes it robust to a change in processing solvent.
Research Organization:
Georgia Inst. of Technology, Atlanta, GA (United States); SLAC National Accelerator Lab., Menlo Park, CA (United States)
Sponsoring Organization:
Dept. of Defense (DoD) (United States); Office of Naval Research (ONR) (United States); USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Grant/Contract Number:
AC02-76SF00515
OSTI ID:
1461805
Journal Information:
Journal of Physical Chemistry. C, Journal Name: Journal of Physical Chemistry. C Journal Issue: 20 Vol. 122; ISSN 1932-7447
Publisher:
American Chemical SocietyCopyright Statement
Country of Publication:
United States
Language:
English

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Cited By (2)

Fullerene derivative induced morphology of bulk heterojunction blends: PIPCP:PC 61 BM journal January 2019
Green-solvent-processable strategies for achieving large-scale manufacture of organic photovoltaics journal January 2019

Figures / Tables (6)

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37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY