Gas expanded polymer process to anneal nanoparticle dispersion in thin films

Journal Article · Tue Apr 21 00:00:00 EDT 2015 · Solar Energy Materials and Solar Cells

DOI:https://doi.org/10.1016/j.solmat.2015.03.024· OSTI ID:1287009

Ambuken, Preejith V. ^[1]; Stretz, Holly A. ^[1]; Dadmun, Mark ^[2]; Michael Kilbey, S. ^[3]

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1. Tennessee Technological Univ., Cookeville, TN (United States)
2. Univ. of Tennessee, Knoxville, TN (United States); Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
3. Univ. of Tennessee, Knoxville, TN (United States)

A spin-coating solution comprising poly(3-hexylthiophene) (P3HT) and phenyl-C61-butyric acid methyl ester (PCBM) nanoparticles used to create organic photovoltaic (OPV) active layers have been shown to adopt a non-uniform concentration profile across the thin film dimension. This inhomogeneous distribution can reduce the efficiency of the device. For our new process, gas expanded polymer (GXP) annealing, is applied to P3HT/PCBM thin film blends, enabling the distribution of the PCBM nanoparticles to be manipulated by varying the GXP processing conditions. Films of 50 nm thickness (nominally) created by spin casting a blend of P3HT mixed with PCBM were annealed by oscillatory GXP and GXP at constant pressure using high pressure CO₂. An increase in P3HT crystallinity (detected by X-ray diffraction and UV-vis spectroscopy) along with a more uniform distribution of PCBM nanoparticles in the thickness dimension, as interpreted from neutron reflectivity measurements, were observed after oscillatory GXP annealing. In addition, static water contact angles suggest that the film/air interface is enriched in PCBM relative to the as-cast film. Finally, these results demonstrate that GXP annealing, which is commercially scalable, can be successfully used to create a uniform distribution of PCBM nanoparticles across the thickness dimension in a P3HT thin film.

• Research Organization: Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Basic Energy Sciences (BES); National Science Foundation (NSF)
• Grant/Contract Number: AC05-00OR22725; EPS-1004083
• OSTI ID: 1287009
• Alternate ID(s): OSTI ID: 1250294
• Journal Information: Solar Energy Materials and Solar Cells, Vol. 140, Issue C; ISSN 0927-0248
• Publisher: Elsevier
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
P3HT
PCBM
Anneal
Organophotovoltaic
Dispersion
CO2
SIZE-SELECTIVE FRACTIONATION
SOLAR-CELLS
ORGANIC PHOTOVOLTAICS
SUPERCRITICAL FLUIDS
CARBON-DIOXIDE
MORPHOLOGY
EFFICIENCY
SOLVENT
LIQUIDS
BLENDS