Electrical and Ammonia Gas Sensing Properties of PQT-12/CdSe Quantum Dots Composite-Based Organic Thin Film Transistors

• Published in: IEEE sensors journal 2018-08, Vol.18 (15), p.6085-6091
• Main Authors: Kumar, Chandan, Rawat, Gopal, Kumar, Hemant, Kumar, Yogesh, Kumar, Amit, Prakash, Rajiv, Jit, Satyabrata
• Format: Article
• Language: English
• Subjects: Cadmium compounds; CdSe QDs; composite film; Gas detectors; gas sensors; II-VI semiconductor materials; Organic thin film transistors; OTFT; PQT-12
• ISSN: 1530-437X; 1558-1748
• DOI: 10.1109/JSEN.2018.2845873

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 SiO 2 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 cm 2 /Vs, -14.4 V, 1.9×10 3 , and 5.2 V/dec while the corresponding values for pristine PQT-12-based OTFT are 1.4× 10 -3 cm 2 /Vs, -22.1 V, 3.6× 10 2 , 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.