Real-time x-ray scattering studies of film formation in high performing small-molecule organic solar cells

Published

May 23, 2015

Author(s)

Sebastian Engmann, Felicia A. Bokel, Andrew Herzing, Hyun W. Ro, Dean DeLongchamp, Lee J. Richter, Claudio Girotto, Bruno Caputo

Abstract

We have studied the influence of the additive diiodoctane on the formation dynamics of high performance bulk heterojunction (BHJ) films based the small molecule donor 7,7'-(4,4bis(2- ethylhexyl)-4H-silolo[3,2-b:4,5-b']dithiophene-2,6-diyl)bis(6-fluoro-5-(5'-hexyl-[2,2'- bithiophen]-5-yl)benzo[c][1,2,5]thiadiazaole), p-DTS(FBTTh2)2. Real-time, in-situ, grazing- incidence X-ray scattering experiments allow us to characterize both the development of crystalline order via wide angle scattering and phase separation via small angle scattering. The performance of small molecule based solar cells has been demonstrated to be extremely sensitive to the specific additive level, unlike analogous polymer systems. We find that the additive both induces increased crystallinity and coarsens the spatial scale of phase separation. The phase separation length scale varies monotonically with additive loading, suggesting the origin of the extreme sensitivity is avoiding excessive coarsening. The additive acts as both a solvent and a plasticizer, controlling the nucleation density and promoting crystal growth.

Citation

Journal of Materials Chemistry A

Volume

3

Pub Type

Journals

Download Paper

https://doi.org/10.1039/C5TA00935A

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Keywords

organic solar cell, photovolatics, fullerene, X-ray diffraction, small-angle scattering

Citation

Engmann, S. , Bokel, F. , Herzing, A. , Ro, H. , DeLongchamp, D. , Richter, L. , Girotto, C. and Caputo, B. (2015), Real-time x-ray scattering studies of film formation in high performing small-molecule organic solar cells, Journal of Materials Chemistry A, [online], https://doi.org/10.1039/C5TA00935A, https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=916457 (Accessed October 11, 2025)