In situ modification of low-cost Cu electrodes for high-performance low-voltage pentacene thin film transistors (TFTs)

We demonstrate low-voltage pentacene thin film transistors (TFTs) using in situ modified low-cost Cu (M-Cu) as source–drain (S/D) electrodes and solution-processed high capacitance (200 nF/cm2) gate dielectrics. Under a gate voltage of −3 V, the device with M-Cu electrodes shows a much higher apparent mobility (1.0 cm2/V s), a positively shifted threshold voltage (−0.62 V), a lower contact resistance (0.11 MΩ) and a larger transconductance (12 μS) as compared to the device with conventional Au electrodes (corresponding parameters are 0.71 cm2/V s, −1.44 V, 0.41 MΩ, and 5.7 μS, respectively). The enhancement in the device performance is attributed to the optimized interface properties between S/D electrodes and pentacene. Moreover, after encapsulation the M-Cu electrodes with a thin layer of Au in the aim of suppressing unfavorable surface oxidation, the electronic characteristics of the device are further improved, and highly enhanced apparent mobility (2.3 cm2/V s) and transconductance (19 μS) can be achieved arising from the increased conductivity of the electrode itself. Our study provides a simple and feasible approach to achieve high performance low-voltage OTFTs with low-cost S/D electrodes, which is desirable for large area applications.

Graphical abstractFigure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Low-voltage pentacene OTFTs with solution-processed dielectric. ► In situ modification of low-cost Cu (M-Cu) as S/D electrodes. ► M-Cu based device show higher performance than Au and Cu. ► Mobility reaches 2.0 cm2/V s with Au encapsulated M-Cu (Au/M-Cu) electrodes. ► The mechanism of this phenomenon is studied in detail.