Ion-modulated transistors on paper using phase-separated semiconductor/insulator blends

Abstract

We have used phase-separated poly(3-hexyltiophene) (P3HT)/poly(L-lactic acid) (PLLA) blends to fabricate low-voltage ion-modulated transistors on a rough paper substrate. The semiconductor and insulator are mixed together in a solution and spin casted onto the paper substrate. Owing to their different solubilities and surface energies the P3HT and PLLA will phase separate vertically during the spinning process creating a thin layer of semiconductor on top of the insulator. This thin semiconductor layer, difficult to achieve by other means on an absorbing paper substrate, creates faster ion-modulated transistors. Using this approach we have created ring-oscillators on paper oscillating at 5 Hz.

Organic transistors on paper: a brief review

“…Owing to the large capacitance of the ion-gel electrolyte, these TFTs also had very low operating voltages (2 V), but a significantly improved on/off current ratio (about 10 6 ). On a 3-stage unipolar ring oscillator, the authors measured a signal propagation delay of 35 ms per stage at a supply voltage of 3 V. 22 In 2011, we showed that the large surface roughness of paper does not necessarily prevent the use of very thin gate dielectrics in the fabrication of organic TFTs. 24 Employing a hybrid gate dielectric consisting of a 3.6 nm-thick layer of oxygen-plasma-grown aluminum oxide (AlO x ) and a 2.1 nm-thick self-assembled monolayer (SAM) of an alkylphosphonic acid, we fabricated bottom-gate, top-contact p-channel and n-channel TFTs and unipolar and complementary inverters directly on the surface of four different types of banknotes.…”

“…The hygroscopic nature of the PVP resulted in a very large gate-insulator capacitance, allowing these TFTs to be operated with voltages of about 1 V. However, due to the significant leakage currents, the TFTs in this initial report had a very small on/off current ratio (about 10). On the same type of paper, Pettersson et al 22 later fabricated P3HT TFTs in which an ion-gel electrolyte obtained by gelation of a triblock copolymer (poly(styrene-block-ethylene oxide-block-styrene); PS-PEO-PS) in an ionic liquid (1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide; [EMIM][TFSI]) 23 was employed as the gate insulator. Owing to the large capacitance of the ion-gel electrolyte, these TFTs also had very low operating voltages (2 V), but a significantly improved on/off current ratio (about 10 6 ).…”

Stability of environmentally friendly paper electronic devices

“…The hysteresis observed in the drain current is as expected for ion‐modulated transistors; lower when measuring in the forward direction and higher in the backward direction. This is a result of the fact that these devices operate electrochemically with the used ICon . The process of reversibly doping and de‐doping the semiconductor during operation is slow due to the internal ICon resistance that hinders the motion of ions.…”

“…The transistor model used in this paper has been demonstrated in previous papers . The transistor is a p‐channel low‐voltage ion‐modulated device, utilizing a solidified sorbitol‐based ionic‐liquid as the electrolyte.…”

“…The two were dissolved (2 wt.%) in chlorobenzene (HPLC, 99,9%), purchased from Sigma–Aldrich, separately and then mixed together in a solution fraction of P3HT:PLLA 20:80. This blend was then drop casted onto the channel area resulting in a thin layer of P3HT on top of a layer of PLLA .…”