Improvement In Device Lifetime Research Articles

Enhancing Light Out-coupling in Perovskite Light-Emitting Diodes through Plasmonic Nanostructures.

Perovskite light-emitting diodes (PeLEDs) have emerged as promising candidates for lighting and display technologies owing to their high photoluminescence quantum efficiency and high carrier mobility. However, the performance of planar PeLEDs is limited by the out-coupling efficiency, predominantly governed by photonic losses at device interfaces. Most notably, the plasmonic loss at the metal electrode interfaces can account for up to 60% of the total loss. Here, we investigate the use of plasmonic nanostructures to improve the light out-coupling in PeLEDs. By integrating these nanostructures with PeLEDs, we have demonstrated an effectively reduced plasmonic loss and enhanced light out-coupling. As a result, the nanostructured PeLEDs exhibit an average 1.5-fold increase in external quantum efficiency and an ∼20-fold improvement in device lifetime. This finding offers a generic approach for enhancing light out-coupling, promising great potential to go beyond existing performance limitations.

Improved device efficiency and lifetime of perovskite light-emitting diodes by size-controlled polyvinylpyrrolidone-capped gold nanoparticles with dipole formation

Herein, an unprecedented report is presented on the incorporation of size-dependent gold nanoparticles (AuNPs) with polyvinylpyrrolidone (PVP) capping into a conventional hole transport layer, poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS). The hole transport layer blocks ion-diffusion/migration in methylammonium-lead-bromide (MAPbBr3)-based perovskite light-emitting diodes (PeLEDs) as a modified interlayer. The PVP-capped 90 nm AuNP device exhibited a seven-fold increase in efficiency (1.5%) as compared to the device without AuNPs (0.22%), where the device lifetime was also improved by 17-fold. This advancement is ascribed to the far-field scattering of AuNPs, modified work function and carrier trapping/detrapping. The improvement in device lifetime is attributed to PVP-capping of AuNPs which prevents indium diffusion into the perovskite layer and surface ion migration into PEDOT:PSS through the formation of induced electric dipole. The results also indicate that using large AuNPs (> 90 nm) reduces exciton recombination because of the trapping of excess charge carriers due to the large surface area.

Transparent organic photovoltaics: A strategic niche to advance commercialization

<h2>Summary</h2> After more than a decade of organic photovoltaics making introductory steps into the market, the scientific and industrial communities keep working toward the consolidation of this technology in the market. The recent development of materials that yield simultaneously high levels of efficiency and transparency brings the opportunity to enter important niche markets, such as transparent photovoltaic windows, in which organic semiconductors might become the best alternative absorber. In this perspective, we provide an overview of the technological progress in organic photovoltaics especially relevant for target semitransparent applications, highlighting key R&D aspects that demand more attention from an industrial and product-development perspective. We conclude that strong effort is needed to develop higher-performing photoactive materials and roll-to-roll compatible interlayer materials and electrodes. Although this is already a significant research focus of the academic community, we identify that reinforcing research effort on topics such as improvement in device lifetime, color portfolio, and module design and efficiency will help in making a significant effect on changing the status of organic photovoltaics from a novel technology to a mature industry.

Strategies to improve the external quantum efficiency of perovskite light-emitting diode

<p indent=0mm>Metal halide perovskite (MHP) has the potential to become the core luminescent material for the next generation of display and lighting equipment due to its excellent photoelectric properties and solution processible. Its unique crystal structure and flexible elemental composition enable it to have adjustable high-color-purity ultra-wide color gamut and bipolar ultra-fast mobility. As early as the 1990s, researchers attempted to prepare perovskite light-emitting diode (PeLED) using layered MHP as the light-emitting material. However, due to the immature membrane forming method and device structure, the device can only light up normally at <sc>110 K.</sc> In 2014, Snaith et al first realized PeLED devices that were normally lit at room temperature. After nearly 5 years’ development, the external quantum efficiency (EQE) of PeLED has been significantly improved, from 0.76% to 20.7% for near-infrared devices and from 0.1% to 20.31% for green devices. At the same time, the highest EQEs for sky-blue devices and blue devices are 12.1% and 9.5%, respectively. In this paper, the factors limiting device EQE are analyzed in principle. The limitation of device EQE can be considered from four factors: Transition selection factor <italic>χ</italic>, charge balance factor <italic>η</italic>_r, optical coupling factor <italic>η</italic>_out and photoluminescence quantum yield <italic>φ</italic>_PL. The photoluminescence quantum yield of perovskite layer is the key factor to determine device EQE, while the charge balance factor and the light coupling factor are the important factors to further improve device EQE. The transition selective factor of perovskite is generally considered to be 100%, which means that both triplet and singlet states of perovskite materials are involved in luminescence. The charge balance factor mainly depends on the choice of electron transport material and hole transport material in the device structure, while the optical coupling factor depends on the morphology of the device film and the external light emission structure in the device. Last but not the least, the photoluminescence quantum yield depends on the type of perovskite material, film quality, and defect passivation. This paper summarizes the strategies reported in the literature to improve EQE of devices from two aspects of “improving the photoluminescence quantum yield of perovskite luminescence layer” and “adjusting device structure to enhance the charge balance factor and the light coupling factor”. In order to obtain the devices with high photoluminescence quantum yield, we first need to prepare high quality perovskite film. On this basis, researchers try to reduce the grain size to reduce the quenching of the excited state at the interface between the transport layers and the perovskite emitting layer. In addition, dimensionality control is a special method to reduce grain size, and has both size effect and funneling effect to change the dominant behavior of radiation recombination in the perovskite emitting layer, from free carriers dominant to exciton dominant. Finally, defect passivation is of great significance to further improve the photoluminescence quantum yield. In addition, this paper also points out the core issues that need to be addressed urgently and the future direction of this region. Blue PeLED that meets the BT2020 standard and the improvement of device lifetime will become the core topics in the future. The development of lead-free perovskite luminescent materials is the only way for PeLED to be commercialized, and will become one of the directions of researchers’ efforts. And exploring high-efficiency white emitting devices under high brightness will become another core topic of this region.

Aqueous Metal Oxide Inks for Modifying Electrode Work Function in Polymer Solar Cells

A method to prepare aqueous metal oxide inks for tuning the work function (WF) of electrodes is demonstrated. Thin films prepared from the metal oxide ink based on vanadium oxide (V2O5) nanoparticles are found to increase the WF of an indium‐tin‐oxide (ITO) electrode. ITO substrates modified with V2O5 films are applied as a hole selective layer (HSL) in polymer solar cells (PSCs) using a poly(3‐hexylthiophene) and [6,6]‐phenyl‐C61 butyric acid methyl ester blend as a photoactive layer. The PSCs prepared with V2O5‐modified ITO show better device performance, achieving a power conversion efficiency of 3.6%, demonstrating 15% enhancement compared to conventional ITO/poly(3,4‐ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT‐PSS) based devices. Furthermore, ITO/V2O5‐modified devices exhibit better ambient stability with 60% improvement in device lifetime than those using PEDOT:PSS as an HSL. This solution‐processable and highly stable WF‐modifying metal oxide film can be a potential alternative material for engineering interfaces in optoelectronic devices.

Facet-passivation processes for the improvement of Al-containing semiconductor laser diodes

The passivation requirements for high-power 980-nm and mid-power 780-nm quantum-well (QW) ridge-waveguide (RWG) Al-containing laser diodes cleaved in air were investigated. In a direct comparison with argon ablation, sulphation, and silicon-barrier-passivation techniques, nitrided facets with a silicon nitride barrier layer exhibited up to an order of magnitude improvement in device lifetime over the next-best method during highly accelerated testing while also maintaining high catastrophic optical damage (COD) or catastrophic optical mirror damage (COMD) thresholds. Well-oxidized facets of 980-nm devices exposed to air for six months were recovered with this process to give reasonable lifetimes (5.66/spl times/10/sup -5/ h/sup -1/ power degradation) during highly accelerated testing.

Reliability of etched-mesa buried-heterostructure semiconductor lasers

This paper reviews the effects of metal-contact-type buried-heterostructure (BH) interfaces and substrate quality on the reliability of BH distributed-feedback (DFB) InGaAsP/InP lasers. For electrical contact, the significant improvement in device lifetime using Au/Ti/Pt/Au p-metallization over Au/Zn/Au will be shown. The temperature and current-density-acceleration factors of the diffusion of Au spiking during life-test aging are estimated. For BH interfaces, performance degradation related to damage on the mesa sidewall generated during the etching process and regrowth processes will be discussed. For the substrate, various failure mechanisms related to the formation and propagation of dark-spot defects (DSD) will be reviewed. The authors discussed various process remedies and show that a thicker buffer may lead to reliability-performance improvement with experimental results. This paper concludes with a brief description of the time-to-failure extrapolation methodology used.

Blue mixed host organic light emitting devices

The lifetime is one of the main issues in the development of organic light-emitting devices (OLEDs). In this paper, we present a new OLED with an emitting layer (EML) based on a blue mixed-host (MH) structure. Compared to the conventional host-dopant system, the MH structure consists of two different hosts and one-dopant materials. Using the structure with different host ratio and fixed dopant concentration, the Commission International de L'Eclairage (CIE 1931) coordinates will shift from (0.17, 0.32) to (0.15, 0.22). The operating lifetime of optimal device is much improved over the heterostructure OLEDs, which shows the lifetime of approximately 110 h with initial luminance of 10000 cd/m2. The luminance reaches 80370 cd/m2 at 10 V, which corresponds to a luminous efficiency of 1.8 cd/A. The significant improvement in device lifetime is attributed to the elimination of the heterojunction interface and the prevention to the formation of fluorescence quenchers. These results demonstrate that the MH structure can extend lifetime without significantly changing the EML with common host material.

Improved hot-carrier reliability of SOI transistors by deuterium passivation of defects at oxide/silicon interfaces

The effect of deuterium on hot-carrier reliability of fully processed 0.18 /spl mu/m silicon-on-insulator (SOI) devices is investigated. The improvement of device lifetime by a factor of 30 is achieved by passivating the interface defects with deuterium instead of hydrogen. The hydrogen/deuterium isotope effect (/spl gamma/), defined as the ratio of generation interface traps of a hydrogenated device to that of a deuterated one, shows strong dependence on the gate stress voltages (V/sub gs/). Increasing V/sub gs/ results in the decrease of /spl gamma/. These results suggest that the breaking of Si-H(D) bonds by channel electrons through the vibrational heating mechanism may play an important role in the degradation of deep submicron SOI devices.

Organic light-emitting diodes with a bipolar transport layer

A structure based on a bipolar transport/emitting layer is proposed and implemented for making organic light-emitting diodes. Compared to the conventional heterojunction organic light-emitting diodes, more than a factor of six improvement in device reliability (a projected operating lifetime of 70 000 h) is achieved in the structure. The significant improvement in device lifetime is attributed to the elimination of the heterointerface present in the conventional devices which greatly affects the device reliability.

Channel hot-carrier stressing of reoxidized nitrided silicon dioxide

The mechanisms of channel hot-carrier-induced degradation in short n-channel MOSFETs with reoxidized nitrided oxide as the gate dielectric are discussed. Charge pumping measurements, supported by observations on the gate voltage dependence of degradation and the power law dependence of Delta g/sub m/ on stress time, demonstrate that virtually no interface trap generation occurs in reoxidized nitrided oxides and that electron trapping is the dominant degradation mechanism. Although electron trapping can be enhanced in these dielectrics, this mechanism is not as important for device degradation as interface trap generation, and the net effect is substantially improved resistance to hot-carrier stress. A three-orders-of-magnitude improvement in device lifetime (versus conventional oxide) is demonstrated. >