1. Annealing-induced phase separation in small-molecular bulk heterojunctions.
- Author
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Wei, Huai-Xin, Li, Yan-Qing, Chen, Xiang-Yu, Lee, Chun-Sing, and Tang, Jian-Xin
- Subjects
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PHASE separation , *HETEROJUNCTIONS , *ELECTRON donor-acceptor complexes , *PHOTOVOLTAIC cells , *X-ray photoelectron spectroscopy , *ANNEALING of crystals - Abstract
Morphology optimization of donor–acceptor bulk heterojunctions at microscopic scale is critical for improving performance of organic photovoltaic devices. Here, effects of thermal annealing on phase separation processes in small-molecular bulk heterojunctions with different geometrical structures (i.e., PTCDA, TiOPc, CuPc and C 60 ) are investigated with ultraviolet and X-ray photoemission spectroscopies. It was identified that post-annealing treatment caused the different degrees of vertical diffusions at the bulk heterojunctions, leading to non-uniform composition distributions. Variations in phase separations are mainly due to the differences in surface energy of the involved materials, which play a crucial role in the intermolecular interactions and the molecular diffusion. Low-surface-energy materials were found to segregate preferentially on the surface for minimizing total energy of the systems. [ABSTRACT FROM AUTHOR]
- Published
- 2014
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