Effect of temperature on hysteresis of dipolar dielectric layer based organic field-effect transistors: A temperature sensing mechanism

This study investigates the effect of measurement temperature on the hysteresis of organic field-effect transistors (OFETs) under vacuum and humidity conditions (-65% RH). OFETs were fabricated using CuPc and PMMA/PVA/Al2O3 tri-layer dielectric materials to possess temperature-sensing capability through the controlled polarization of polar dielectric (PVA) layer with excellent stability, enhanced performance over a wide range of temperature. We report a novel temperature sensing mechanism of the OFETs by exploiting the temperature dependence of hysteresis, mobility and bias-stress. At room temperature, the device exhibited hole mobility of 0.004 cm(2)/V s and 0.016 cm(2)/Vs, threshold voltage of -3.8 V and -3.7 V under vacuum and ambient conditions, respectively. Over the temperature range of 150-370 K, the variation of mobility found to follow the Arrhenius behavior, supporting hopping charge transport. At 370 K, the mobility is enhanced by five times while switching the ambient from vacuum to humidity. However, there is a great enhancement in the mobility of similar to 30 times at 370 K compared to room temperature under ambient conditions. Under both the conditions, we observed a systematic variation of hysteresis from clock wise to anti-clock wise direction and its amount. Bias-stress experiments showed the enhanced stability in the performance of the OFETs under different ambient condition with temperature. We have demonstrated how the systematic polarization of polar dielectric layer can be exploited to fabricate OFET based temperature sensor, which is highly sensitive to temperature variation within 250 K-370 K ranges. The response/recovery times were found to be 25 and 15 s, respectively. (C) 2017 Elsevier B.V. All rights reserved.