The Semiconductor/Conductor Interface Piezoresistive Effect in an Organic Transistor for Highly Sensitive Pressure Sensors

Abstract

Pressure sensor is one of the most fascinating and important components of E-skin that possesses unique abilities to imitate, enhance, and replace the human's tactile sensation. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16] Among the different kinds of pressure sensors, [17][18][19][20][21][22][23][24][25][26][27][28][29][30] piezoresistive sensors generally have simple structures and easy read-out characteristics, which make them highly promising for application. [31][32][33][34] However, on the other hand, the simple output signal (current or resistance) presents difficulty to identify the complex and multiple stimuli. As for the organic field-effect transistor (OFET)-based sensors, the unique current amplification function of transistor makes it ideal candidate for sensing weak signals, and their multiple output parameters (source-drain current, threshold voltage, current on/off ratio, subthreshold swing) enable it to distinguish complex signals. [35][36][37] Furthermore, every component of OFETs including gate electrode, dielectric layer, semiconductor layer, and drain/source electrodes can be probably used as active layer of sensors, [38,39] which provides more possibilities for integration of multiple sensing. [40][41][42][43][44] In some reported sensors, tuning dielectric capacitance of OFET by pressure is mainly used as the basic working principle. Bao and co-workers pioneered in using microstructured poly(dimethylsiloxane) (PDMS) as dielectric of OFET for sensing pressure with sensitivity of 0.55 kPa −1 . [22] Zhu and co-workers utilized a suspended gate for construction of pressure sensor with sensitivity of 192 kPa −1 . [30] However, the tuning of capacitance in OFET may suffer from the risk of impurity or breakdown. As stated above, all components of OFET might be used for the pressure sensors, but OFET-based pressure sensors using semiconductor and source/ drain electrodes have not been reported so far.In OFETs, the contact interface between semiconductor and source/drain electrodes determines the charge injection efficiency and thus greatly influences the device performance, which therefore provides a model for pressure sensing if the contact quality can be tuned by pressure with an appropriate device structure. Piezoresistive sensor with roughened contact interface provides inspiration, but the active components of conventional piezoresistive sensor generally consist of one or more kinds of conducting materials since the low bulk resistivity of conducting materials may enable the contact resistance to dominate the sensor device and therefore produce The piezoresistive pressure sensor, a kind of widely investigated artificial device to transfer force stimuli to electrical signals, generally consists of one or more kinds of conducting materials. Here, a highly sensitive pressure sensor based on the semiconductor/conductor interface piezoresistive effect is successfully demonstrated by using organic transistor geometry. Because of the efficient combination of the piezoresistive effect and f...

Understanding the Meniscus‐Guided Coating Parameters in Organic Field‐Effect‐Transistor Fabrications

“…Organic semiconductor thin films serve as critical layers in organic field‐effect‐transistors (OFETs), which determine the performance of the OFETs. Motivated by diverse OFET applications in functional electronics, such as memory devices, integrated circuits, sensors and etc., comprehensive studies of organic thin films are indispensable toward the high‐performance OFETs for commercial applications . As a low‐cost and fast organic thin film fabrication method, solution processable meniscus‐guided coating (MGC) has attracted tremendous attention and achieved impressive progresses on different OFET properties in recent years .…”

Recent Advances in Flexible Field‐Effect Transistors toward Wearable Sensors

“…A real sensing set was then introduced as a Digital Tactile (DiTact) sensing system with a wearable glove to demonstrate the frequency changes of the voltage signal after applying pressure onto the wearable system ( Figure a). Inspired by this pyramidal microstructured design for resistive sensing, Wang et al [ 112 ] developed a piezoresistive‐type F‐FET sensor that used the same structural design in the device. However, a novel operating mechanism was proposed, based on the contacts between the semiconductor and conductive electrodes.…”

“…f) Tunable sensitivity of the sensor under different gate voltages from −60 to −10 V. Reproduced with permission. [ 112 ] Copyright 2015, Wiley‐VCH.…”

Synergistic Resistance Modulation toward Ultrahighly Sensitive Piezoresistive Pressure Sensors

“…Remarkably, the sensitivity derived from Figure 2b achieved an ultrahigh value of 11 668.6 kPa −1 in Figure 2c, which guarantees the high‐precision detection. The calibration curve in Figure 2c is comprised of three regimes which respectively represent three deformation processes, [ 48 ] as presented in Figure S2 (Supporting Information), the number of contact points between pyramids and PEDOT:PSS film increases under tiny pressure range for “S 0 ,” the transformation of pyramids/PEDOT:PSS film interface from point‐to‐face contact to face‐to‐face contact for “S 1 ,” the gradual saturated deformation of pyramids under large pressure for “S 2 .” A huge progress in sensitivity was demonstrated by virtue of the unique synergistic resistance modulation effect. In respect of repeatability, we tested the repeated current response under pressures of 80, 250, 400, 550, and 600 Pa, as shown in Figure 2d, where the sensing signal shows excellent repeatability and stability.…”