Enhanced Direct White Light Emission Efficiency in Quantum Dot Light‐Emitting Diodes via Embedded Ferroelectric Islands Structure

Abstract

White light emission is of great importance in our daily life as it is the primary source of light indoor and outdoor as well as day and night. Among various materials and lighting technologies, intensive efforts have been made to quantum dots based-light-emitting diode (QD-LEDs, or QLEDs) because of outstanding optical properties, facile synthesis, and bandgap tunability of QDs. Despite the fact that QLEDs are able to present various colors in a visible range, realizing efficient direct white light emission is a challenge as white light emission can only be achievable through stacking and patterning of QD films or mixing of different sizes of QDs. This inevitably involves energy band mismatch at interfaces, leading to degradation of device performance. Here, a new effective method to improve white QLED performances through embedding a ferroelectric islands structure is introduced, which induces an electric field to effectively modulate the energy band at the junction interface. The formation of a favorable energy landscape leads to efficient charge transport, improved radiative recombination, and consequently high external quantum efficiency in the white QLEDs. In addition, it is demonstrated that this new approach is proved to be effective in different color temperatures ranging from 3000 to over 120 000 K.

Controlled p-Type Doping of MoS2 Monolayer by Copper Chloride

“…To implement the TMDC monolayers for practical electronic device applications, the device properties need to be tailored to show the desired output characteristics of electronic devices. One way to achieve the desired device characteristics is through doping [ 3 , 15 , 16 , 17 , 18 , 19 ]. The doping of 2D materials is recognized to be the key to precisely controlling their fundamental properties, based on the history of the contemporary Si or III–V-based semiconductors.…”

Ferroelectric Field Effect Induced Charge Carrier Transport Modulation at Quantum Dot Solar Cell Heterojunction Interface

“…Energy band levels of each layer were determined using previous reports. ,− An inset image in Figure a shows the chemical structure of P­(VDF-TrFE) where the electric dipoles due to negative fluorine and a positive hydrogen atom induce an electric field when they are aligned . QDSCs were fabricated by a layer-by-layer (LBL) spin-coating method following our previous reports. , In particular, an island structure P­(VDF-TrFE) layer was introduced in order to ensure charge carrier transport as the P­(VDF-TrFE) is a natural insulator. − The P­(VDF-TrFE) island structures could be formed by using two strategies. First, by controlling the concentration of a P­(VDF-TrFE) solution, we could achieve a P­(VDF-TrFE) film with a wider channel area to conduct photogenerated charges as shown in Figure S1a,b in the Supporting Information (SI).…”

Solution-processed colloidal quantum dots for light emission

“…The second way of making WQLEDs, which holds more promise for future development, is via white EL emission obtained through the electroluminescent action of combined blue, green and red QDs. (59,71,94,95). Another interesting avenue of research is the use of QDs in communicating technologies.…”

“…[97][98][99][100][101] The second way of making WQLEDs, which holds more promise for future development, is via white EL emission obtained through the electroluminescent action of combined blue, green and red QDs. 53,78,102,103 Another interesting avenue of research is the use of QDs in communication technologies. QLEDs and QD lasers have shown improvement upon existing lightemitting devices, however, using QDs in visible light communication has not yet produced devices comparable to current radiofrequency methods.…”