Poly(p-phenyleneacetylene)-based light-emitting diodes

摘要

A study of poly(p-phenyleneacetylene) (PPA)-based light-emitting diodes (LEDs) is described and discussed. The LEDs were fabricated by spin-coating the indium tin oxide (ITO) coated glass substrate with the 2,5-dibutoxy or 2,5- dihexoxy derivative of PPA dissolved in toluene, followed by evaporation of a layer of Ca and Al or Al only on the polymer. As the spin-coating, drying, and operation of the diodes was performed in air with no heat sink, the Ca/Al devices degraded within a few minutes at room temperature, but were stable in a He ambient at low temperatures. However, it was noted that baking the diodes coated with an Al layer for 2 - 6 hours at 150$DGR@C in a flow of dry N$-2$/ markedly increased their performance. However, no improvement was achieved by baking the polymer laser prior to metallization. It is therefore believed that the baking process removes significant defects from the polymer/metal interface. The nature of these results is discussed in terms of bulk defects as well as defects at the ITO/polymer and polymer/metal interfaces.