TY - JOUR
T1 - Tuning domain size and crystallinity in isoindigo/PCBM organic solar cells via solution shearing
AU - Gu, Kevin L.
AU - Zhou, Yan
AU - Gu, Xiaodan
AU - Yan, Hongping
AU - Diao, Ying
AU - Kurosawa, Tadanori
AU - Ganapathysubramanian, Baskar
AU - Toney, Michael F.
AU - Bao, Zhenan
N1 - Funding Information:
X.G., Y.D., M.F.T., and Z.B. acknowledge support by the Department of Energy , Office of Energy Efficiency & Renewable Energy , Bridging Research Interactions through the collaborative Development Grants in Energy (BRIDGE) program under Contract No. DE-FOA-0000654-158. Y.Z., T.K., and Z.B. acknowledge the Office of Naval Research under Award No. N00014-14-1-0142 . H.Y. acknowledges the National Science Foundation Materials Genome Initiative under Grant No. 1434799 . B.G. acknowledges partial financial support from the National Science Foundation under Grant no. 1435587 and 1149365 . K.L.G. was supported by the Department of Defense (DoD) through the National Defense Science & Engineering Graduate Fellowship (NDSEG) Program. Portions of this work were carried out at Beamline 11.0.1.2 at the Advanced Light Source, which is supported by the Director, Office of Science, Office of Basic Energy Sciences, of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231 , and at Beamline 11-3 of the Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, which is supported by the U.S. Department of Energy , Office of Science, Office of Basic Energy Sciences under Contract No. DE-AC02-76SF00515 .
Publisher Copyright:
© 2016 Elsevier B.V.
PY - 2017
Y1 - 2017
N2 - Despite having achieved the long sought-after performance of 10% power conversion efficiency, high performance organic photovoltaics (OPVs) are still mostly constrained to lab scale devices fabricated by spin coating. Efforts to produce printed OPVs lag considerably behind, and the sensitivity to different fabrication methods highlights the need to develop a comprehensive understanding of the processing-morphology relationship in printing methods. Here we present a systematic experimental investigation of a model low bandgap polymer/fullerene system, poly-isoindigo thienothiophene/PC61BM, using a lab-scale analogue to roll-to-roll coating as the fabrication tool in order to understand the impact of processing parameters on morphological evolution. We report that domain size and polymer crystallinity can be tuned by a factor of two by controlling the temperature and coating speed. Lower fabrication temperature simultaneously decreased the phase separation domain size and increased the relative degree of crystallinity in those domains, leading to improved photocurrent. We conclude that domain size in isoindigo/PCBM is dictated by spontaneous phase separation rather than crystal nucleation and growth. Furthermore we present a model to describe the temperature dependence of domain size formation in our system, which demonstrates that morphology is not necessarily strictly dependent on the evaporation rate, but rather on the interplay between evaporation and diffusion during the printing process.
AB - Despite having achieved the long sought-after performance of 10% power conversion efficiency, high performance organic photovoltaics (OPVs) are still mostly constrained to lab scale devices fabricated by spin coating. Efforts to produce printed OPVs lag considerably behind, and the sensitivity to different fabrication methods highlights the need to develop a comprehensive understanding of the processing-morphology relationship in printing methods. Here we present a systematic experimental investigation of a model low bandgap polymer/fullerene system, poly-isoindigo thienothiophene/PC61BM, using a lab-scale analogue to roll-to-roll coating as the fabrication tool in order to understand the impact of processing parameters on morphological evolution. We report that domain size and polymer crystallinity can be tuned by a factor of two by controlling the temperature and coating speed. Lower fabrication temperature simultaneously decreased the phase separation domain size and increased the relative degree of crystallinity in those domains, leading to improved photocurrent. We conclude that domain size in isoindigo/PCBM is dictated by spontaneous phase separation rather than crystal nucleation and growth. Furthermore we present a model to describe the temperature dependence of domain size formation in our system, which demonstrates that morphology is not necessarily strictly dependent on the evaporation rate, but rather on the interplay between evaporation and diffusion during the printing process.
KW - Isoindigo
KW - Morphology evolution
KW - Organic photovoltaics
KW - Phase separation
KW - X-ray scattering
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U2 - 10.1016/j.orgel.2016.10.033
DO - 10.1016/j.orgel.2016.10.033
M3 - Article
AN - SCOPUS:84997112224
VL - 40
SP - 79
EP - 87
JO - Organic Electronics: physics, materials, applications
JF - Organic Electronics: physics, materials, applications
SN - 1566-1199
ER -