Page 209 - Organic Electronics in Sensors and Biotechnology

186 Chapter Five

50
OLED
Double shielded, coumarin-doped Alq 3
40

30
I 0 /I Shielded, Alq OLED
3
20

10 Unshielded, Alq OLED
3
0
0 20 40 60 80 100
% Oxygen

FIGURE 5.16 SV plots using unshielded and shielded structurally integrated
O sensors: OLED/PdOEP:PS/thin fi lm Si-based PD. (Reprinted with permission
2
from Ref. 81, “Integrated Photoluminescence-Based Sensor Arrays: OLED
Excitation Source/Sensor Film/Thin-Film Photodetector,” SPIE 2007.)

The latter higher sensitivity was achieved in part by shielding
the electromagnetic noise generated by the pulsed current through the
OLED and wiring when using lock-in detection. In one approach,
81
the shielding was achieved by placing a grounded ITO/glass, as
shown in Fig. 5.17, over the OLED. This sensitivity is still lower than
the sensitivity of the [Alq -based OLED]/[PdOEP:PS] module
3
obtained with a PMT, and the thin-film PD could only monitor O in
2
the I mode (due to the PD’s slow speed), but it still demonstrates the
potential ultimate success of the three-component integrated plat-
form. As the measurement of τ is beneficial over I, the development
of the thin-film PDs focuses currently on obtaining a detailed under-
standing of the factors affecting their speed, in an attempt to shorten
their response time.

ITO

Glass

OLED pixel

FIGURE 5.17 OLED shielding confi guration (not to scale), which resulted in
signifi cantly improved S . (Reprinted with permission from Ref. 81, “Integrated
g
Photoluminescence-Based Sensor Arrays: OLED Excitation Source/Sensor
Film/Thin-Film Photodetector,” SPIE 2007.)