Controlling Spontaneous Orientation Polarization in Organic Semiconductors -- The Case of Phosphine Oxides

Abstract

Upon film growth by physical vapor deposition, the preferential orientation of polar organic molecules can result in a non-zero permanent dipole moment (PDM) alignment, causing a macroscopic film polarization. This effect, known as spontaneous orientation polarization (SOP), was studied in the case of different phosphine oxides. We investigate the control of SOP by molecular design and film-growth conditions. Our results show that using less polar phosphine oxides with just one phosphor-oxygen bond yields an exceptionally high degree of SOP with the so-called giant surface potential (slope) reaching more than 150mV/nm in a neat BCPO film grown at room temperature. Additionally, by altering the evaporation rate and the substrate temperature, we are able to control the SOP magnitude over a broad range from 0 to almost 300mV/nm. Diluting BCPO in a non-polar host enhances the PDM alignment only marginally, but combining temperature control together with dipolar doping can result in almost perfectly aligned molecules with more than 80% of their PDMs standing upright on the substrate on average.

References in corpus (2)

• Controlling Structure and Properties of Vapor-Deposited Glasses of Organic Semiconductors: Recent Advances and Challenges
• Vapor deposition rate modifies anisotropic glassy structure of an anthracene-based organic semiconductor

Cited by in corpus (3)

• Enhancement of Spontaneous Orientation Polarization in Organic Semiconductor Mixtures
• Generic behavior of ultrastability and anisotropic molecular packing in co-deposited organic semiconductor glass mixtures
• Spontaneously Formed Orientation Polarization Thin Films for Engineering Organic-Organic Interfaces