Light-Emitting Quantum Dot Transistors: Emission at High Charge Carrier Densities

Abstract

For the application of colloidal semiconductor quantum dots in optoelectronic devices, for example, solar cells and light-emitting diodes, it is crucial to understand and control their charge transport and recombination dynamics at high carrier densities. Both can be studied in ambipolar, light-emitting field-effect transistors (LEFETs). Here, we report the first quantum dot light-emitting transistor. Electrolyte-gated PbS quantum dot LEFETs exhibit near-infrared electroluminescence from a confined region within the channel, which proves true ambipolar transport in ligand-exchanged quantum dot solids. Unexpectedly, the external quantum efficiencies improve significantly with current density. This effect correlates with the unusual increase of photoluminescence quantum yield and longer average lifetimes at higher electron and hole concentrations in PbS quantum dot thin films. We attribute the initially low emission efficiencies to nonradiative losses through trap states. At higher carrier densities, these trap states are deactivated and emission is dominated by trions.

Molecular Orientation‐Dependent Bias Stress Stability in Bottom‐Gate Organic Transistors Based on an n‐Type Semiconducting Polymer

“…The electrical properties of the organic transistors were determined at room temperature in a dark environment under a N 2 atmosphere using a Keithley 4200-SCS Semiconductor Parameter Analyzer. The fi eld-effect mobilities ( µ ) and the threshold voltages ( V th ) were estimated in the saturation regime ( V DS = 60 V) according to the following equation [ 52 ] I…”

Work-Function Engineering in Lead Sulfide and Cadmium Sulfide Quantum Dots incorporated into Zeolite Y using Ion Exchange

“…Quantum dots (QDs) are nanometer‐scale semiconductor materials that have physical dimensions smaller than the exciton Bohr radius, which causes them to exhibit a quantum confinement effect . QDs display size‐tunable physical and chemical properties completely distinct from their parent bulk compounds, and can, therefore, be exploited as transistors, solar cells, light‐emitting diodes (LEDs), and diode lasers . In general, routes for synthesizing QDs have involved two classes of techniques: first, top‐down processing methods, including molecular beam epitaxy (MBE), ion implantation, e‐beam lithography, and X‐ray lithography; and second, a bottom‐up approach in which colloidal QDs are prepared by self‐assembly in solution following a chemical reduction …”

Defect-induced photoluminescence of strontium titanate and its modulation by electrostatic gating

“…These states are plausible to be hole as well as electron trap levels forming non-radiative recombination sites which lower the intrinsic PL of STO in the direct band gap state. 38 These positive and negative recombination centers can efficiently be deactivated by the variation of relative position of the Fermi level using negative and positive gate fields respectively [38][39][40][41] . We expect the filling of electron trap states while the gate field is swung positive and the passivation of hole trap states when the gate field is swung negative.…”