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Inversion of Dominant Polarity in Ambipolar Polydiketopyrrolopyrrole with Thermally Removable Groups
Author(s) -
Lee Junghoon,
Han AReum,
Hong Jayeon,
Seo Jung Hwa,
Oh Joon Hak,
Yang Changduk
Publication year - 2012
Publication title -
advanced functional materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 6.069
H-Index - 322
eISSN - 1616-3028
pISSN - 1616-301X
DOI - 10.1002/adfm.201200940
Subject(s) - ambipolar diffusion , materials science , thermogravimetric analysis , electron mobility , fourier transform infrared spectroscopy , organic semiconductor , field effect transistor , analytical chemistry (journal) , optoelectronics , transistor , chemical engineering , electron , organic chemistry , chemistry , quantum mechanics , voltage , engineering , physics
A narrow bandgap polymeric semiconductor, BOC‐PTDPP , comprising alkyl substituted diketopyrrolopyrrole (DPP) and tert ‐butoxycarbonyl ( t ‐BOC)‐protected DPP, is synthesized and used in organic field‐effect transistors (OFETs). The polymer films are prepared by solution deposition and thermal annealing of precursors featuring thermally labile t ‐BOC groups. The effects of the thermal cleavage on the molecular packing structure in the polymer thin films are investigated using thermogravimetric analysis (TGA), UV‐vis spectroscopy, atomic force microscopy (AFM), Fourier transform infrared (FT‐IR) spectroscopy, and X‐ray diffraction (XRD) analysis. Upon utilization of solution‐shearing process, integrating the ambipolar BOC‐PTDPP into transistors shows p ‐channel dominant characteristics, resulting in hole and electron mobilities as high as 1.32 × 10 −2 cm 2 V −1 s −1 and 2.63 × 10 −3 cm 2 V −1 s −1 , which are about one order of magnitude higher than those of the drop‐cast films. Very intriguingly, the dominant polarity of charge carriers changes from positive to negative after the thermal cleavage of t ‐BOC groups at 200 °C. The solution‐sheared films upon subsequent thermal treatment show superior electron mobility ( μ e = 4.60 × 10 −2 cm 2 V −1 s −1 ), while the hole mobility decreases by one order of magnitude ( μ h = 4.30 × 10 −3 cm 2 V −1 s −1 ). The inverter constructed with the combination of two identical ambipolar OFETs exhibits a gain of ∼10. Reported here for the first time is a viable approach to selectively tune dominant polarity of charge carriers in solution‐processed ambipolar OFETs, which highlights the electronically tunable ambipolarity of thermocleavable polymer by simple thermal treatment.