Low-temperature annealed PbS quantum dot films for scalable and flexible ambipolar thin-film-transistors and circuitsElectronic supplementary information (ESI) available: The field-emission scanning electron microscope images, the transfer characteristics and on-/off-currents up to 300 °C, the variation of IDS with positive bias stress, the transfer and gain characteristics of a CMOS inverter at VDD of 10 V, and the Scherrer equation based grain size from GIAXRD. See DOI: 10.1039/c4tc01624f

• Main Authors: Jo, Chan Ho, Kim, Jae Hyun, Kim, Jaekyun, Kim, Jiwan, Oh, Min Suk, Kang, Moon Sung, Kim, Myung-Gil, Kim, Yong-Hoon, Ju, Byeong-Kwon, Park, Sung Kyu
• Format: Article
• Language: English
• ISSN: 2050-7526; 2050-7534
• DOI: 10.1039/c4tc01624f

Thiocyanate (SCN)-treated lead sulfide (PbS) quantum dot thin-film-transistors (QD TFTs) and CMOS-compatible circuits were fabricated on a flexible substrate via a scalable photolithography process. Spectroscopic and electrical investigations demonstrated that the thermal treatments induce ligand decomposition and densification of the QD arrays at around 170 °C. High temperature annealing above 200 °C induces an aggregation of the QD particles, resulting in a degradation of device performance, such as the field-effect mobility and the on-/off-current ratio. It is also noted that the surface defects which act as charge carrier traps are increased with the annealing temperature, possibly due to the decomposition of the SCN leading to an aggregation of the QD particles. On the basis of the experimental results, bottom-gate and bottom-contact ambipolar PbS QD TFTs with an electron/hole mobility of 0.47/0.43 cm 2 V −1 s −1 and CMOS inverter circuits with gains of >14 V at a supply bias of 10 V were successfully fabricated on spin-on thin plastic substrates. In-depth investigations on thermal annealing of PbS QDs for high performance flexible inorganic devices and circuits were carried out.