Two common hole transporting materials, N,N′-di(1-naphthyl)-N,N′-diphenyl-(1,1′-biphenyl)-4,4′-diamine (NPD) and tris(4-carbazoyl-9-ylphenyl)amine (TCTA) are separated and purified using thermal gradient sublimation. Their sublimation rates are proportional to the tube diameter squared and inversely proportional to the distance from the source boat to the deposition region. The deposition of these materials exponentially decays with distance down the tube. A theory predicting these results is derived. This theory suggests that diffusion and surface capture are the dominant steps in this purification, not processes in the source boat. It provides a rationale for improving the separation between multiple components and suggests routes for producing larger quantities of these materials.
Bibliographical noteFunding Information:
Funding and support for this work was provided by The Dow Chemical Company . The authors thank Jacob Crosthwaite and Lynn Stiehl for the vapor pressure data and acknowledge useful discussions with Dr. Timothy Frank. RJH is a member of The Dow Chemical Company Technical Advisory Board.
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- Low pressure vapor transport
- Organic electronics
- Organic semiconductors