Abstract
This study investigates the remarkable reduction in the threshold voltage (VT) of pentacene-based thin film transistors with pentacene/copper phthalocyanine (CuPc) sandwich configuration. This reduction is accompanied by increased mobility and lowered sub-threshold slope (S). Sandwich devices coated with a 5 nm layer of CuPc layer are compared with conventional top-contact devices, and results indicate that VT decreased significantly from −20.4 V to −0.2 V, that mobility increased from 0.18 cm2/Vs to 0.51 cm2/Vs, and that S was reduced from 4.1 V/dec to 2.9 V/dec. However, the on/off current ratio remains at 105. This enhanced performance could be attributed to the reduction in charge trap density by the incorporated CuPc layer. Results suggest that this method is simple and effectively generates pentacene-based organic thin film transistors with high mobility and low VT.
Highlights
This study investigates the remarkable reduction in the threshold voltage (VT) of pentacene-based thin film transistors with pentacene/copper phthalocyanine (CuPc) sandwich configuration
Sandwich devices coated with a 5 nm layer of CuPc layer are compared with conventional top-contact devices, and results indicate that VT decreased significantly from −20.4 V to −0.2 V, that mobility increased from 0.18 cm2/Vs to 0.51 cm2/Vs, and that S was reduced from 4.1 V/dec to 2.9 V/dec
increase of drain current (Id) increased by a factor of approximately 4.5 at Vd = −100 V and Vg = −100 V when a 5 nm CuPc layer was introduced into the pentacene/CuPc sandwich devices (Figs. 2(a) and 2(b))
Summary
Organic thin film transistors (OTFTs) have attracted much attention because they are low cost, operate under low temperatures, are compatible with plastic substrates, and have much potential for application.[1,2,3,4] The development of high-performance OTFTs has progressed significantly; the mobility (>1 cm2/Vs) and on/off current ratio (>105) of these OTFTs are comparable with those of amorphous silicon thin film transistors (TFTs).[5,6,7,8] In practice, OTFTs remain problematic in terms of the high threshold voltage (VT; a few tens of volts).[7,8,9,10] To lower power consumption, low VT is a basic requirement. 2(c) and 2(d), we determine the performance levels of the top-contact and sandwich pentacene-based OTFTs in terms of field-effect mobility (μFET), VT, sub-threshold slope (S), and on/off current ratio (Ion/Ioff).
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