GO:PEDOT:PSS for High-Performance Green Phosphorescent Organic Light-Emitting Diode

The Optimization of Hole Injection Layer in Organic Light-Emitting Diodes

Organic light-emitting diodes (OLEDs) are widely recognized as the forefront technology for displays and lighting technology. Now, the global OLED market is nearly mature, driven by the rising demand for superior displays in smartphones. In recent years, numerous strategies have been introduced and demonstrated to optimize the hole injection layer to further enhance the efficiency of OLEDs. In this paper, different methods of optimizing the hole injection layer were elucidated, including using a suitable hole injection material to minimize the hole injection barrier and match the energy level with the emission layer, exploring new preparation methods to optimize the structure of hole injection layer, and so on. Meanwhile, this article can help people to understand the current research progress and the challenges still faced in relation to the hole injection layer in OLEDs, providing future research directions to enhance the properties of OLEDs.

Fabrication and Characterization of Humidity Sensors Based on Graphene Oxide-PEDOT:PSS Composites on a Flexible Substrate

In this paper, we present a simple, fast, and cost-effective method for the large-scale fabrication of high-sensitivity humidity sensors on flexible substrates. These sensors consist of a micro screen-printed capacitive structure upon which a sensitive layer is deposited. We studied two different structures and three different sensing materials by modifying the concentration of poly(3,4-ethylenedioxythiophene)/polystyrene sulfonate (PEDOT:PSS) in a graphene oxide (GO) solution. The results show that the aggregation of the PEDOT:PSS to the GO can modify its electrical properties, boosting the performance of the capacitive sensors in terms of both resistive losses and sensitivity to relative humidity (RH) changes. Thus, in an area less than 30 mm2, the GO/PEDOT:PSS-based sensors can achieve a sensitivity much higher (1.22 nF/%RH at 1 kHz) than other similar sensors presented in the literature which, together with their good thermal stability, time response, and performance over bending, demonstrates that the manufacturing approach described in this work paves the way for the mass production of flexible humidity sensors in an inexpensive way.

Effects of PEDOT:PSS:GO composite hole transport layer on the luminescence of perovskite light-emitting diodes

Perovskite light-emitting diodes (PeLEDs) employing CH₃NH₃PbBr₃ as the emission layer (EML) and graphene oxide (GO) doped PEDOT:PSS as the hole transport layer (HTL) were prepared and characterized. GO doped in PEDOT:PSS can lead to the increased work function of HTL and lower the hole injection barrier at the HTL/CH₃NH₃PbBr₃ interface, which facilitates the hole injection. Meanwhile, the optimized GO amount in PEDOT:PSS can help to reduce the quenching of luminescence occurring at the interface between HTL and perovskite. The luminance and current efficiency reach the maximum values of 3302 cd m⁻² and 1.92 cd A⁻¹ in PeLED with an optimized GO ratio (0.3), which increase by 43.3% and 73.0% in comparison with the undoped device, respectively. The enhanced luminescence of PeLEDs was caused by the combined effects of enhanced hole injection efficiency and the suppressed exciton quenching occurring at the HTL/EML interface. These results indicate that the introduction of traditional two-dimensional materials is a reasonable method for designing the structure of PeLEDs.

Perovskite light-emitting diodes (PeLEDs) employing CH₃NH₃PbBr₃ as the emission layer (EML) and graphene oxide (GO) doped PEDOT:PSS as the hole transport layer (HTL) were prepared and characterized.

Improved Charge Injection and Transport of Light-Emitting Diodes Based on Two-Dimensional Materials

Light-emitting diodes (LEDs) are considered to be the most promising energy-saving technology for future lighting and display. Two-dimensional (2D) materials, a class of materials comprised of monolayer or few layers of atoms (or unit cells), have attracted much attention in recent years, due to their unique physical and chemical properties. Here, we summarize the recent advances on the applications of 2D materials for improving the performance of LEDs, including organic light emitting diodes (OLEDs), quantum dot light emitting diodes (QLEDs) and perovskite light emitting diodes (PeLEDs), using organic films, quantum dots and perovskite films as emission layers (EMLs), respectively. Two dimensional materials, including graphene and its derivatives and transition metal dichalcogenides (TMDs), can be employed as interlayers and dopant in composite functional layers for high-efficiency LEDs, suggesting the extensive application in LEDs. The functions of 2D materials used in LEDs include the improved work function, effective electron blocking, suppressed exciton quenching and reduced surface roughness. The potential application of 2D materials in PeLEDs is also presented and analyzed.

Organic devices based on nickel nanowires transparent electrode

Herein, we demonstrate a facile approach to synthesize long nickel nanowires and discuss its suitability to replace our commonly used transparent electrode, indium-tin-oxide (ITO), by a hydrazine hydrate reduction method where nickel ions are reduced to nickel atoms in an alkaline solution. The highly purified nickel nanowires show high transparency within the visible region, although the sheet resistance is slightly larger compared to that of our frequently used transparent electrode, ITO. A comparison study on organic light emitting diodes and organic solar cells, using commercially available ITO, silver nanowires, and nickel nanowires, are also discussed.

Fine-tuning optical and electronic properties of graphene oxide for highly efficient perovskite solar cells

Simplifying the process of fine-tuning the electronic and optical properties of graphene oxide (GO) is of importance in order to fully utilize it as the hole interfacial layer (HIL). We introduced silver trifluoromethanesulfonate (AgOTf), an inorganic chemical dopant, that tunes and controls the properties of single-layered GO films synthesized by chemical vapor deposition. The morphology, work function, mobility, sheet resistance, and transmittance of the GO film were systematically tuned by various doping concentrations. We further developed a solution-processable low-temperature hole interfacial layer (HIL) poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (

PEDOT

PSS):AgOTf-doped GO HIL in highly efficient perovskite solar cells. The

PEDOT

PSS:AgOTf-doped GO HIL grants the desirable charge-collection in the HIL allowing the entire device to be prepared at temperatures less than 120 °C. The fabricated perovskite solar cells utilize a rigid substrate and demonstrate compelling photovoltaic performance with a power conversion efficiency (PCE) of 11.90%. Moreover, flexible devices prepared using a polyethylene terephthalate (PET)/ITO demonstrate a PCE of 9.67%, while ITO-free flexible devices adopting PET/aluminum doped zinc oxide (AZO)/silver (Ag)/AZO demonstrate a PCE of 7.97%. This study shows that the

PEDOT

PSS:AgOTf-doped GO HIL has significant potential to contribute to the development of low-cost solar cells.

Graphene oxide grafted polyethylenimine electron transport materials for highly efficient organic devices

We propose a mixture of graphene oxide and polyethylenimine ethoxylate as an efficient electron transport layer for organic solar cells.