Low-temperature annealed PbS quantum dot films for scalable and flexible ambipolar thin-film-transistors and circuits

Abstract

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 cm² 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.