Page 195 - Organic Electronics in Sensors and Biotechnology

172 Chapter Five

40
Day 1
Day 30
30

τ 0 /τ 20

10

0
0 20 40 60 80 100
% O 2

FIGURE 5.4 Stern-Volmer plots of a gas-phase O sensor obtained at 23°C
2
using an [Alq OLED]/[PtOEP-doped PS fi lm] sensor module measured daily
3
for 30 days. The fi lm was prepared by drop casting a solution containing
PtOEP:PS at a ratio of 1:15.

250

200

τ 0 /τ 150

100

50 0

0
0 20 40 60 80 100
% O 2
FIGURE 5.5 The SV plot at 23°C of a PdOEP-based gas-phase O sensor
2
17
excited by a rubrene-doped Alq OLED. The sensing fi lm was prepared by
3
drop-casting; it is doped with TiO particles. The SV plot is linear up to ~40%
2
O . (Reprinted from Ref. 17. Copyright 2007, with permission from Elsevier.)
2
OLED bias pulse amplitude was 20 V, its width was 100 μs, and its
repetition rate was 25 Hz; τ was determined by averaging the PL
decay curves over 1000 pulses. As clearly seen, the SV plots deviate
from linearity, and the sensitivity decreased slightly from ~40 on day
1 to ~37 on day 30, with the main changes occurring at high O levels.
2