Electrical and ammonia gas sensing properties of PQT-12/CdSe quantum dots composite-based organic thin film transistors

Abstract

The electrical and ammonia gas sensing properties of poly (3, 3''-dialkylquaterthiophene) (i.e., PQT-12) and CdSe quantum dots (QDs) composite-based back-gated organic thin film transistors (OTFTs) fabricated on SiO2 coated heavily doped p-Si substrates by solution method have been investigated in this paper. The properties of pristine PQT-12 and PQT-12/CdSe QDs composite films have been investigated by transmission electron microscopy and atomic force microscopy. To investigate the effect of colloidal CdSe QDs on the characteristics of PQT-12-based OTFTs, the performance of pristine PQT-12-based OTFT has been compared with that of the PQT-12/CdSe QDs composite-based OTFT. The field effect mobility, threshold voltage, on/off current ratio, and subthreshold swing of the PQT-12/CdSe QDs composite-based OTFT are 4.2 × 10-3 cm2/Vs, -14.4 V, 1.9 × 103, and 5.2 V/dec while the corresponding values for pristine PQT-12-based OTFT are 1.4 × 10-3 cm2/Vs, -22.1 V, 3.6 × 102, and 7.9 V/dec, respectively. When the devices are exposed to ammonia gas, an estimated gas response of 51% is obtained for PQT-12/CdSe QDs composite-based OTFT whereas the gas response of 41% is achieved for the pristine PQT-12 OTFT sensor. The improved gas response in the PQT-12/CdSe QDs composite-based OTFT is attributed to enhanced charge transfer due to the CdSe QDs as compared with the pristine PQT-12-based OTFT. © 2001-2012 IEEE.