M. Meier et al., METAL INSULATOR POLYMER - LEDS BASED ON PPV, Molecular crystals and liquid crystals science and technology. Section A, Molecular crystals and liquid crystals, 283, 1996, pp. 197-202
We investigated the current-voltage (I-V) and electroluminescence (EL)
characteristic of metal/polymer and metal/insulator/polymer (MIP) LED
s based on poly (1,4-phenylene vinylene) (PPV). The I-V- and EL charac
teristics of the MIP structures display a pronounced dependence of the
insulator thickness and we measure an increase of the quantum efficie
ncy of more than a factor of 40 at an A1O(x) layer thickness of 3-5nm
The device characteristic is qualitatively understood within inorganic
metal/insulatos/semiconductor (MIS) theory and can be explained by a
voltage dependent barrier for minority carrier injection in connection
with a hole blocking barrier at the PPV/insulator interface. With MIP
structures we reveal external quantum efficiencies up to 0.01%, compa
rable to values achieved on monolayer Ca LEDs. The MIP structures, how
ever have the advantage, that a more stable device performance is obta
ined.