Influence of Substrate on Crystallization in Polythiophene/fullerene Blends

Journal Article · Sat Dec 31 04:00:00 EST 2011 · Solar Energy Materials and Solar Cells

DOI:https://doi.org/10.1016/j.solmat.2010.12.035· OSTI ID:1042313

He, C; Germack, D; Kline, J; Delongchamp, D; Fischer, D; Snyder, C; Toney, M; Kushmerick, J; Richter, L

The nanoscale morphology of the active layer in organic, bulk heterojunction (BHJ) solar cells is crucial to device performance. Often a combination of casting conditions and post deposition thermal treatment is used to optimize the morphology. In general, the development of microscopic crystals is deleterious, as the exciton diffusion length is {approx}10 nm. We find that the microscopic crystallization behavior in polythiophene/fullerene blends is strongly influenced by the substrate on which the BHJ is cast. With a silicon oxide substrate, the crystal nucleation density is high and significant crystallization occurs at a temperature of 140 C. On more hydrophobic substrates, significantly higher temperatures are required for observable crystallization. This difference is attributed to the interfacial segregation of the PCBM, controlled by the substrate surface energy. The substrate dependence of crystallization has significant implications on the fullerene crystal growth mechanisms and practical implications for device studies.

• Research Organization: BROOKHAVEN NATIONAL LABORATORY (BNL)
• Sponsoring Organization: USDOE SC OFFICE OF SCIENCE (SC)
• DOE Contract Number: AC02-98CH10886
• OSTI ID: 1042313
• Report Number(s): BNL--97991-2012-JA
• Journal Information: Solar Energy Materials and Solar Cells, Journal Name: Solar Energy Materials and Solar Cells Journal Issue: 5 Vol. 95; ISSN SEMCEQ; ISSN 0927-0248
• Country of Publication: United States
• Language: English

Related Subjects

14 SOLAR ENERGY
36 MATERIALS SCIENCE
CASTING
CRYSTAL GROWTH
CRYSTALLIZATION
CRYSTALS
DENSITY
DEPOSITION
DIFFUSION LENGTH
EQUIPMENT
EXCITONS
FULLERENES
HETEROJUNCTIONS
LAYERS
MORPHOLOGY
NUCLEATION
PERFORMANCE
SEGREGATION
SILICON OXIDES
SOLAR CELLS
SUBSTRATES
SURFACE ENERGY