A chlorinated barium titanate-filled polymer composite with a high dielectric constant and its application to electroluminescent devices

• Published in: Journal of materials chemistry. C, Materials for optical and electronic devices Materials for optical and electronic devices, 2013-01, Vol.1 (33), p.5078-5083
• Main Authors: Kim, Jin-Young, Kim, Hoonbae, Kim, TaeYoung, Yu, Seonmi, Suk, Ji Won, Jeong, Taewon, Song, Sunjin, Bae, Min Jong, Han, Intaek, Jung, Donggeun, Park, Shang Hyeun
• Format: Article
• Language: English
• Subjects: Chlorination; Devices; Dielectric constant; Doping; Electroluminescence; Luminance; Particulate composites; Phosphors
• ISSN: 2050-7526; 2050-7534
• DOI: 10.1039/c3tc30767k

We have studied the effect of chlorination on the dielectric performance of a barium titanate (BTO)-polymer film. Functionalization of BTO powder particles with chlorine (Cl) atoms and/or Cl-containing functional groups was achieved by a simple treatment using chlorinated solvents. The chlorinated BTO (Cl-BTO) particles were incorporated into a cyanoethyl-based polymer and the mixture was spin-coated to produce a composite film. The dielectric constant of the composite film with Cl-BTO was as high as 208 at a frequency of 10 Hz, showing a 2.5-fold increase in dielectric constant compared to composites composed of the neat BTO and the cyanoethyl-based polymer at a frequency of 10 Hz. The observed dramatic increase in dielectric constant would be caused by the interfacial polarization due to the p-type doping effect resulting from the presence of strong electronegative Cl atoms. Given a relatively high dielectric constant, composite films with Cl-BTO were further exploited as a dielectric layer in an inorganic electroluminescence (EL) device. The luminance of the EL device with Cl-BTO was 4090 cd m super(-2) at a frequency of 1 kHz, showing a 2.03-fold increase in luminance compared to that with the untreated BTO. The improved performance of the EL device is attributed to a high dielectric constant of the composite films that allow for efficient charge carrier tunneling into the phosphor and therefore enhanced luminance and efficiency.