Polyethylenimine Ethoxylated Layer Research Articles

Perovskite Photo-Sensors with Solution-Processed TiO2 under Low Temperature Process and Ultra-Thin Polyethylenimine Ethoxylated as Electron Injection Layer

A perovskite photo-sensor is promising for a lightweight, thin, flexible, easy-to-coat fabrication process, and a higher incident photon-to-current conversion efficiency. We have investigated perovskite photo-sensors with a solution-processed compact TiO2 under a low-temperature process and an ultra-thin polyethylenimine ethoxylated (PEIE) as an electron injection layer. The TiO2 film is grown from an aqueous solution of titanium tetrachloride (TiCl4) at 70 °C by a chemical bath deposition method. For an alternative process, the ultra-thin PEIE is spin coated on the TiO2 film. Then, the perovskite layer is deposited on the substrate by the one- or two-step methods in the glovebox. Next, a hole transport layer of 2,2,7,7-tetrakis(N,N-di-p-methoxyphenylamine)-9, 9-spiro-bifluorene (Spiro-OMeTAD) solution is spin coated. The fabricated device structure is a photodiode structure of FTO/TiO2/(without or with) PEIE/(one- or two-step) perovskite layer/Spiro-OMeTAD/Au. For the sensing characteristics, a ratio of photo-to-dark-current density was 2.88 × 104 for the device with PEIE layer. In addition, a power-law relationship is discussed.

Performance and stability improvement in organic photovoltaics using non-toxic PEIE interfacial layers

The improvement in current density–voltage characteristics and external quantum efficiency of organic photovoltaics with non-toxic polyethylenimine ethoxylated (PEIE) as a modified layer between the electron transport layer and the active layer were demonstrated. The mechanisms of carrier transport, photon generation current, and the carrier recombination influenced by the PEIE layer were systematically studied. An extra PEIE layer was demonstrated having a shorter relaxation time via pump-probe spectroscopy, which provides better charge transfer ability. From capacitance-voltage measurement, the effective capacitance of the device increase with an addition PEIE layer, corresponding to the increase of accumulation carriers generated at the interfaces. Furthermore, electrochemical impedance spectroscopy elucidated that the PEIE layer can reduce the carrier recombination probability in the devices. As a result, the lifetime of the devices with a PEIE layer is improved as compared to the devices without PEIE layer. • A non-toxic PEIE layer was demonstrated as having a shorter carrier relaxation time via pump-probe spectroscopy, which provides better charge transfer ability in OPV. •The non-toxic PEIE layer not only provides larger effective capacitance of the device resulting from amount of accumulation carriers generated at the interfaces, but also reduces the carrier recombination probability. •The stability of the devices with a PEIE layer is also improved as the device performance can keep within 90 % compared to its original PCE values after 1400-h measurement in a nitrogen-filled glove box without encapsulation.

Polyethylenimine-ethoxylated dual interfacial layers for highly efficient and all-solution-processed inverted quantum dot light-emitting diodes

Inverted quantum dot light-emitting diodes (QLEDs) were fabricated through all-solution processing by sandwiching quantum dot (QD) emitting layers (EMLs) between dual polyethylenimine-ethoxylated (PEIE) layers. First, a PEIE layer as EML protecting layer (EPL) was formed on a QD EML to protect the EML from the hole transport layer (HTL) solvents and to facilitate the formation of a well-organized structure in the all-solution-processed inverted QLEDs. Second, another PEIE layer was introduced as an electron-blocking layer (EBL) on the zinc oxide (ZnO) electron transport layer (ETL) and effectively suppressed the excessive electron injection to the QD EML, thereby enhancing device efficiency.

High-Performance Quantum Dot-Light-Emitting Diodes with a Polyethylenimine Ethoxylated-modified Emission layer

ABSTRACT Colloidal quantum dots (QDs) are emerging as one of the most promising candidates due to their unique optical and physical properties. Solution-processed QD-based light-emitting diodes (QLEDs) have been extensively studied and developed for next-generation displays and solid-state lighting. The most practical approach to improve device performance is to optimize charge transport and charge balance in the recombination region. Here, we applied polyethylenimine ethoxylated (PEIE) with low-work function modifiers on top of the quantum dot emissive layer to reach a better charge balance and devices was characterized. Our QLED with a 5.4 nm PEIE layer exhibited a maximum luminance of 41,440 cd/m2 and current efciency of 4.9 cd/A, which are signifcantly more than 2.3 times greater than that of QLED without PEIE.

Reduce the hysteresis effect with the PEIE interface dipole effect in the organic-inorganic hybrid perovskite CH3NH3PbI3-xClx solar cell

Abstract Power conversion efficiency (PCE) of CH3NH3PbI3 perovskite solar cells has been developed rapidly, it reached the 22.1%. However, the anomalous hysteresis found in I-V measurements can cause an inaccurate estimation of the efficiency. In this article, we fabricated the ITO/PEDOT:PSS/CH3NH3PbI3-xClx/ PCBM/PEIE/Al structure perovskite solar cell, we inserted an interface layer of Polyethylenimine ethoxylated (PEIE) into solar cell device between the PCBM and aluminum (Al) electrode, the electrical filed induce photoluminescence (PL) quenching experiment and capacitance-voltage characteristic both demonstrate that the PEIE layer exists an interface dipole effect in the perovskite solar cell device, it can effectively reduce the hysteresis effect in the I-V measurement, and greatly increase the solar cell's efficiency from the 10.93%–14.46%. Utilizing the photoinduction dielectric response technology, we further found that the interface dipole effect increased the built-in electrical field, and enhanced the charge carrier transport properties, consequently, increased the short-circuit current (Jsc). On the other hand, the interface dipole effect decreased the concentration of defect on the CH3NH3PbI3-xClx surface, and made the charge injection barrier to increasing at the electrode and perovskite interface, leading to enhance the open-circuit voltage (Voc). In addition, the diminution of defect could further increase more effective electron transport channels, leading to the more charge carriers transport toward to the corresponding electrode, and increased the solar cell's Fill Factor (FF). Therefore, the addition PEIE interface layer in the perovskite solar cell not only can remove the hysteresis effect but also develop the high PCE perovskite solar cell. We hope the interface dipole effect as an effective methods can greatly promote and develop high efficiency and stable perovskite solar cells.

Improving the stability and efficiency of perovskite light-emitting diodes via an insulating layer of polyethylenimine ethoxylated

The highly stable and efficient perovskite light-emitting diodes (PeLEDs) via applying an insulating layer of polyethylenimine ethoxylated (PEIE) are fabricated. The PeLED consisted of an ultrathin PEIE layer exhibits 90.6% of initial maximum luminance after 2 h and can still emit light after 8 days. Meanwhile, by realizing the morphology improvement of MAPbBr3 and more balanced charge injection of perovskite film, a high efficiency PeLEDs with a maximum luminance of 914.5 cd/m2 and a maximum current efficiency of 0.28 cd/A at a bias of 8.1 V are achieved. This work not only proposes a concise and effective approach for the significant improvement of PeLEDs stability, but also opens a high potential route for the practical application of high efficiency PeLEDs.

Device architecture for efficient, low-hysteresis flexible perovskite solar cells: Replacing TiO2 with C60 assisted by polyethylenimine ethoxylated interfacial layers

We here report methylammonium lead-iodide-based perovskite solar cells (psSCs) in which a TiO2 layer (a de-facto electron transport layer of psSCs) is replaced with a layer of C60 evaporated onto indium tin oxide layers covered with polyethylenimine ethoxylated (PEIE) layers. Unlike TiO2 layers requiring a high-temperature sintering, C60 is deposited while the substrate is held at room temperature, making it compatible with various plastic substrates for flexible psSCs. The PEIE layers are shown to play key roles, not only as an electron-collecting interfacial layer but also as a surface modifier that helps maintain the integrity of the C60 layers during spin-coating of the perovskite active layers. Using the proposed device architecture, we demonstrate flexible psSCs that exhibit power conversion efficiency as high as 13.3% with low hysteresis.

Effect of polyelectrolyte interlayer on efficiency and stability of p-i-n perovskite solar cells

In this work, we demonstrated a high performance planar heterojunction perovskite solar cell with the polyethylenimine ethoxylated (PEIE) interlayer. By adopting a less polar solvent for PEIE, enhanced device performance and uniformity are achieved. The power conversion efficiency (PCE) of the best device increases by 22% compared to the reference device and reaches 14.82% with JSC of 19.45mA/cm2, VOC of 1.00V, and FF of 76.31% under AM 1.5G 100mW/cm2 light illumination. The UPS measurement shows that the PEIE layer can effectively decrease the energy offset between PCBM and metal electrode. The recombination mechanism was explored by measuring VOC and JSC at various light intensities from 100 to 0.1mW/cm2. It shows that the PEIE layer can suppress the trap-assisted recombination for the devices. The enhancement of the probability of the carriers collection also shows that the recombination is reduced by the PEIE interlayer. Moreover, it is found PEIE layer can improve the stability of the device.

High-efficiency hybrid organic–inorganic light-emitting devices

We report efficient red, orange, green and blue organic–inorganic light emitting devices using light emitting polymers and polyethylenimine ethoxylated (PEIE) interlayer with the respective luminance efficiency of 1.3, 2.7, 10 and 4.1cdA−1, which is comparable to that of the analogous conventional devices using a low work-function metal cathode. This is enabled by the enhanced electron injection due to the effective reduction of the ZnO work-function by PEIE, as well as hole/exciton-blocking function of PEIE layer. Due to the benign compatibility between PEIE and the neighboring organic layer, the novel phosphorescent organic–inorganic devices using solution-processed small molecule emissive layer show the maximum luminance efficiency of 87.6cdA−1 and external quantum efficiency of 20.9% at 1000cdm−2.

High-efficiency inverted polymer solar cells controlled by the thickness of polyethylenimine ethoxylated (PEIE) interfacial layers.

In this work, we investigate the effect of the thickness of the polyethylenimine ethoxylated (PEIE) interface layer on the performance of two types of polymer solar cells based on inverted poly(3-hexylthiophene) (P3HT):phenyl C61-butryric acid methyl ester (PCBM) and thieno[3,4-b]thiophene/benzodithiophene (PTB7):[6,6]-phenyl C71-butyric acid methyl ester (PC71BM). Maximum power conversion efficiencies of 4.18% and 7.40% were achieved at a 5.02 nm thick PEIE interface layer, for the above-mentioned solar cell types, respectively. The optimized PEIE layer provides a strong enough dipole for the best charge collection while maintaining charge tunneling ability. Optical transmittance and atomic force microscopy measurements indicate that all PEIE films have the same high transmittance and smooth surface morphology, ruling out the influence of the PEIE layer on these two parameters. The measured external quantum efficiencies for the devices with thick PEIE layers are quite similar to those of the optimized devices, indicating the poor charge collection ability of thick PEIE layers. The relatively low performance of devices with a PEIE layer of thickness less than 5 nm is the result of a weak dipole and partial coverage of the PEIE layer on ITO.

Investigation of Solution-Processed Ultrathin Electron Injection Layers for Organic Light-Emitting Diodes

We study two types of water/alcohol-soluble aliphatic amines, polyethylenimine (PEI) and polyethylenimine-ethoxylated (PEIE), for their suitability as electron injection layers in solution-processed blue fluorescent organic light-emitting diodes (OLEDs). X-ray photoelectron spectroscopy is used to determine the nominal thickness of the polymer layers while ultraviolet photoelectron spectroscopy is carried out to determine the induced work-function change of the silver cathode. The determined work-function shifts are as high as 1.5 eV for PEI and 1.3 eV for PEIE. Furthermore, atomic force microscopy images reveal that homogeneous PEI and PEIE layers are present at nominal thicknesses of about 11 nm. Finally, we solution prepare blue emitting polymer-based OLEDs using PEI/PEIE in combination with Ag as cathode layers. Luminous efficiency reaches 3 and 2.2 cd A(-1), whereas maximum luminance values are as high as 8000 and 3000 cd m(-2) for PEI and PEIE injection layers, respectively. The prepared devices show a comparable performance to Ca/Ag OLEDs and an improved shelf lifetime.

Carrier transport of inverted quantum dot LED with PEIE polymer

An inverted-type quantum-dot light-emitting-diode (QD LED), employing low-work function organic material polyethylenimine ethoxylated (PEIE) as electron injection layer, was fabricated by all solution processing method, excluding anode electrode. From transmission electron microscopy (TEM) and scanning electron microscopy (SEM) studies, it was confirmed that CdSe@ZnS QDs with 7nm size were uniformly distributed as a monolayer on PEIE layer. In this inverted QD LED, two kinds of hybrid organic materials, [poly (9,9-di-n-octyl-fluorene-alt-benzothiadiazolo)(F8BT)+poly(N,N′-bis(4-butylphenyl)-N,N′-bis(phenyl)benzidine (poly-TPD)] and [4,4′-N,N′-dicarbazole-biphenyl (CBP)+poly-TPD], were adopted as hole transport layer having high highest occupied molecular orbital (HOMO) level for improving hole transport ability. At a low-operating voltage of 8V, the device emits orange and red spectral radiation with high brightness up to 2450 and 1420cd/m2, and luminance efficacy of 1.4cd/A and 0.89cd/A, respectively, at 7V applied bias. Also, the carrier transport mechanisms for the QD LEDs are described by using several models to fit the experimental I–V data.