Electroluminescence and photoluminescence of conjugated polymer films prepared by plasma enhanced chemical vapor deposition of naphthalene

摘要

Polymer light-emitting devices were fabricated utilizing plasma polymerizedthin films as emissive layers. These conjugated polymer films were prepared byRF Plasma Enhanced Chemical Vapor Deposition (PECVD) using naphthalene asmonomer. The effect of different applied powers on the chemical structure andoptical properties of the conjugated polymers was investigated. The fabricateddevices with structure of ITO/PEDOT:PSS/ plasma polymerized Naphthalene/Alq3/Alshowed broadband Electroluminescence (EL) emission peaks with center at 535-550nm. Using different structural and optical tests, connection between polymerschemical structure and optical properties under different plasma powers hasbeen studied. Fourier transform infrared (FTIR) and Raman spectroscopiesconfirmed that a conjugated polymer film with a 3-D cross-linked network wasdeveloped. By increasing the power, products tended to form as highlycross-linked polymer films. Photoluminescence (PL) spectra of plasma polymersshowed different excimerc emissions, resulted from crosslinked architecture.Further analysis showed an interesting change in dominance of excimericemissions by increasing the power. In fact, as the plasma power increased, theoptical properties showed two different domains; up to 200 w, EL, PL and UV-Visspectra red-shifted and broadened significantly. At higher powers, a reversebehavior was observed. Also, the relation between the film structure and plasmaspecies was investigated using Optical Emission Spectroscopy (OES).