Simulation study of blue InGaN multiple quantum well light-emitting diodes with different hole injection layers

InGaN-based light-emitting diodes with p-GaN and p-A1GaN hole injection layers are numerically studied using the APSYS simulation software. The simulation results indicate that light-emitting diodes with p-A1GaN hole injection layers show superior optical and electrical performance, such as an increase in light output power, a reduction in current leakage and alleviation of efficiency droop. These improvements can be attributed to the p-A1GaN serving as hole injection layers, which can alleviate the band bending induced by the polarization field, thereby improving both the hole injection efficiency and the electron blocking efficiency.

Improvement of Performance of Organic Light-Emitting Diodes with Both a MoO3 Hole Injection Layer and a MoO3 Doped Hole Transport Layer

We improve the performance of organic light-emitting diodes （OLEDs） with both a MoO3 hole injection layer （HIL） and a MoO3 doped hole transport layer （HTL）, and present a systematical and comparative investigation on these devices. Compared with OLEDs with only MoO3 HIL or MoO3 doped HTL, OLEDs with both MoO3 HIL and MoO3 doped HTL show superior performance in driving voltage, power efficiency, and stability. Based on the typical NPB/Alq3 heterojunction structure, OLEDs with both MoO3 HIL and MoO3 doped HTL show a driving voltage of 5.4 V and a power efficiency of 1.41 lm/W for 1000 cd/m2, and a lifetime of around 0. 88 h with an initial luminance of 5268 cd/m2 under a constant current of 190 mA/cm2 operation in air without encapsulation. While OLEDs with only MoO3 HIL or MoO3 doped HTL show higher driving voltages of 6.4 V or 5.8 V and lower power efficiencies of 1.201m/W or 1.341m/W for 1000cd/m2, and a shorter lifetime of 0.33 or 0.60h with an initial luminance of around 5122 or 5300cd/m2 under a constant current of 200 or 216mA/cm2 operation. Our results demonstrate clearly that using both MoO3 HIL and MoO3 doped HTL is a simple and effective approach to simultaneoasly improve both the hole injection and transport efficiency, resulting from the lowered energy barrier at the anode interface and the increased hole carrier density in MoO3 doped HTL.

Performance improvement of GaN-based light-emitting diode with a p-InAlGaN hole injection layer

The characteristics of a blue light-emitting diode （LED） with a p-InA1GaN hole injection layer （HIL） is analyzed numerically. The simulation results indicate that the newly designed structure presents superior optical and electrical performance such as an increase in light output power, a reduction in current leakage and alleviation of efficiency droop. These improvements can be attributed to the p-InA1GaN serving as hole injection layers, which can alleviate the band bending induced by the polarization field, thereby improving both the hole injection efficiency and the electron blocking efficiency.

Accelerating directional charge separation via built-in interfacial electric fields originating from work-function differences

In this work,a hierarchical porous SnS_(2)/rGO/TiO_(2)hollow sphere heterojunction that allows highly-efficient light utilization and shortening distance of charge transformation is rationally designed and synthesized.More importantly,an rGO interlayer is successfully embedded between the TiO_(2)hollow sphere shells and outermost SnS_(2)nanosheets.This interlayer functions as a bridge to connect the two light-harvesting semiconductors and acts as a hole injection layer in the tandem heterojunction.The induced built-in electric fields on both sides of the interface precisely regulate the spatial separation and directional migration of the photo-generated holes from the light-harvesting semiconductor to the rGO hole injection interlayer.These synergistic effects greatly prolong the lifetime of the photo-induced charge carriers.The optimized tandem heterojunction with a 2 wt%rGO loading demonstrate enhanced visible-light-driven photocatalytic activity for Rhodamine B(RhB)dye degradation(removal rate:97.3%)and Cr(VI)reduction(removal rate:97.09%).This work reveals a new strategy for the rational design and assembly of hollow-structured photocatalytic materials with spatially separated reduction and oxidation surfaces to achieve excellent photocatalytic performance.

Increased work function in PEDOT:PSS film under ultraviolet irradiation

An increase of work function （0.3 eV） is achieved by irradiating poly（3,4-ethylenedioxythiophene）：poly（styrene sul- fonate） （PEDOT：PSS） film in vacuum with 254-nm ultraviolet （UV） light. The mechanism for such an improvement is investigated by photoelectron yield spectroscopy, X-ray photo electron energy spectrum, and field emission technique. Sur- face oxidation and composition change are found as the reasons for work function increase. The UV-treated PEDOT：PSS film is used as the hole injection layer in a hole-only device. Hole injection is improved by UV-treated PEDOT：PSS film without baring the enlargement of film resistance. Our result demonstrates that UV treatment is more suitable for modifying the injection barrier than UV ozone exposure.