RESUMEN
We demonstrate a novel structure for a quantum-dot light-emitting diode (QD-LED) with wide-range colour-tuneable pixels, fabricated via full solution processing. The proposed device has a symmetrical structure produced via stacking of an inverted-structure diode with a green QD emission layer (EML) and normal-structure diode with a red QD EML. It is an electron-only device; however, a charge generation layer in the middle of the device generates holes for the formation of excitons. Depending on the polarity of the applied voltage, either the bottom inverted unit or the top normal unit is operated, thereby emitting green or red light, respectively. The working mechanism of the device is investigated via analysis of the charge generation mechanism and carrier transport path. In addition, the colour tunability is verified using a simple alternating current (AC) driving scheme; the duty cycle modulation of the AC signal enables fine colour adjustment over a broad range, from pure green to pure red. Thus, our colour-tuneable QD-LED with vertically stacked independently operated sub-pixels can open a promising pathway towards cost-effective ultra-high-resolution displays.
RESUMEN
Graphene-based transistors are promising devices in the evaluation of carrier density in biological analytes. We report on the design and fabrication of a graphene-based field-effect transistor for monitoring and assessing the interaction between the coagulation factors based on the charge carrier density in a blood sample. When biochemical reactions occurred during the coagulation cascade process, a dopant effect was noticed on the graphene surface by the change in Dirac point voltage values. Additional experiments were performed using blood samples treated with activators (vitamin K, calcium chloride, and thromboplastin reagent) and inhibitors (heparin drugs) to evaluate the selectivity of the graphene field-effect transistor devices. Since the transfer characteristic curves presented divergent behaviours for different levels of procoagulants and anticoagulants, the measurements showed that the devices can assess changes in the concentrations of factors that inhibit or accelerate the cascade process when using untreated and treated samples. Reproducibility was verified by testing samples from different sources. To the best of our knowledge, this study is the first to demonstrate the potential of graphene in monitoring the hemostasis process through the analysis of the electrical properties of human whole blood.
