120 1C annealed polymer thin film exhibits less organized
morphology. As the annealing temperature was increased to
160 and 200 1C, the morphology becomes more organized and
exhibits well aligned B1.5 mm wide microstripes. Sharpening of
the 2y peak at 5.271 at 200 1C annealing also supports this
observation. Under a higher resolution, it is evident that the
microstripes are composed of firmly held crystalline nanograins,
which are considered favorable for efficient intergranular charge
transport. Ideal HOMO–LUMO energy levels, strong intra-
molecular interactions and preferred molecular organization
make PDPP-FBF a very suitable candidate for high performance
ambipolar OFETs with respectable charge carrier mobility.
We have demonstrated that furan is a promising building
block for high performance semiconducting polymers for use
in ambipolar OTFTs. With the incorporation of an electron-
withdrawing furan-containing DPP moiety into benzothiadia-
zole the resulting polymer PDPP-FBF has shown high and
balanced hole and electron mobilities of 0.20 cm2 Vꢀ1 sꢀ1 and
0.56 cm2 Vꢀ1 sꢀ1, respectively. These results clearly reveal that
the furan substituted DPP is a promising conjugated building
block for designing novel high performance ambipolar semi-
conductors for organic electronic applications.
Fig. 3 Output and transfer characteristic in the hole and electron enhance-
ment modes of a PDPP-FBF based ambipolar OTFT annealed at 200 1C
on the OTS treated p ꢁ Si/SiO2 substrate. The hole and electron transfer
curves were derived at drain voltages (VD) of ꢀ70 V and +70 V respectively.
Device dimensions: channel length = 180 mm; channel width = 3 mm.
Notes and references
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Fig. 4 (i) Effect of preannealing at various temperatures on hole and
electron mobility of PDPP-FBF based ambipolar OTFT, (ii) AFM
phase images of PDPP-FBF thin films annealed at (A) 120 1C, (B and D)
160 1C and (C and E) 200 1C on OTS treated p ꢁ Si/SiO2 substrates.
ambipolar polymer PDPP-TBT reported earlier.1a In addition, hole
and electron mobilities of 0.61 cm2 Vꢀ1 sꢀ1 and 0.67 cm2 Vꢀ1 sꢀ1
have been measured for 200 1C annealed samples at gate voltage
ꢀ80 V. The effect of annealing temperature on charge carrier
mobility is shown in Fig. 4(i). An on-to-off current ratio (Ion/Ioff) of
B103 is calculated for all of the devices.
8 (a) Y. Li, P. Sonar, S. P. Singh, W. Zeng and M. S. Soh, J. Mater.
Chem., 2011, 21, 10829; (b) P. Sonar, S. P. Singh, E. L. Williams, Y. Li,
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AFM was conducted to elucidate the effects of annealing on
morphology. The AFM height images in Fig. 4(ii) show that the
c
This journal is The Royal Society of Chemistry 2012
Chem. Commun., 2012, 48, 8383–8385 8385