Polyethylenimine Ethoxylated Research Articles

A Polymeric Two-in-One Electron Transport Layer and Transparent Electrode for Efficient Indoor All-Organic Solar Cells.

Transparent electrodes (TEs) are vital in optoelectronic devices, enabling the interaction of light and charges. While indium tin oxide (ITO) has traditionally served as a benchmark TE, its high cost prompts the exploration of alternatives to optimize electrode characteristics and improve device efficiencies. Conducting polymers, which combine polymer advantages with metal-like conductivity, emerge as a promising solution for TEs. This work introduces a two-in-one electron transport layer (ETL) and TE based on films of polyethylenimine ethoxylated (PEIE)-modified poly(benzodifurandione) (PBFDO). These PEIE-modified PBFDO layers exhibit a unique combination of properties, including low sheet resistance (130 Ω sq-1), low work function (4.2 eV), and high optical transparency (>85% in the UV-vis-NIR range). In contrast to commonly used poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS), the doping level of PBFDO remains unaffected by the PEIE treatment, as verified through UV-vis-NIR absorption and X-ray photoelectron spectroscopy measurements. When employed as a two-in-one ETL/TE in organic solar cells, the PEIE-modified PBFDO electrode exhibits performance comparable to conventional ITO electrodes. Moreover, this work demonstrates all-organic solar cells with record-high power conversion efficiencies of >15.1% under indoor lighting conditions. These findings hold promise for the development of fully printed, all-organic optoelectronic devices.

Unraveling the Photovoltage Formation Mechanism in Indium-Tin Oxide Branched Nanowires/Poly(3-Hexylthiophene) Photorechargeable Supercapacitors.

Photorechargeable supercapacitors are promising next-generation renewable energy storage devices. Previously, a hybrid structure consisting of indium-tin oxide branched nanowires (ITO BRs) and poly(3-hexylthiophene) (P3HT) was demonstrated as a photorechargeable supercapacitor. However, the formation mechanism of photovoltage has not been studied. Herein, we experimentally investigated the photovoltage-determining parameters in the ITO BRs/P3HT photorechargeable supercapacitor by inserting a polyethylenimine ethoxylated (PEIE) interlayer or adding a phenyl-C61-butyric acid methyl ester (PCBM) electron acceptor. Coating the PEIE interlayer on ITO BRs decreased the work function by 0.5 eV and hindered the hole extraction from P3HT to ITO BRs, leading to interfacial recombination and a decrease in photovoltage. On the other hand, the addition of PCBM promoted the charge transfer of the electrons from P3HT to PCBM, enhanced the redox reaction at the PCBM/electrolyte interface, and reduced the number of accumulated electrons, leading to a decreased photovoltage. From these results, we found that two key parameters determine the photovoltage and charge storage capability; one is the interfacial recombination at the ITO BRs/P3HT interface and the other is the redox reaction at the P3HT/electrolyte interface.

Aqueous PEIE Soaking on ZnO for Ultraviolet Light Activation-Free Organic Photovoltaic Modules.

Ultraviolet (UV) light is typically needed to activate inverted organic photovoltaics (OPVs) with zinc oxide (ZnO) as electron transporting layer (ETL)for higher efficiency. However, UV light is a major cause for the degradation of organic active layers in OPVs. This is a contradiction that UV light activation enhances the efficiency but UV illumination deteriorates the stability. It is important to solve this contradiction to develop UV light activation-free OPV devices. Herein, a method of aqueous polyethylenimine ethoxylated (PEIE) soaking on ZnO is reported to realize UV light activation-free OPV devices. The S-shape in current density-voltage (J-V) characteristics of devices tested without UV light activation is eliminated through the treatment of aqueous PEIE soaking on ZnO. The treatment reduces the oxygen adsorbates, which is confirmed by Kelvin probe and X-ray photoelectron spectroscopy. A 10.08 cm2 organic photovoltaic module with the treated ZnO asETL showed high photovoltaic performance: VOC = 5.68 V, JSC = 2.7 mAcm-2, FF = 75.1%, and POutput = 11.5 mWcm-2 tested with the UV filter (light intensity of 0.788 sun). UV light activation is not needed for the modules to obtain high efficiency.

Advancing Detectivity and Stability of Near-Infrared Organic Photodetectors via a Facile and Efficient Cathode Interlayer.

Near-infrared (NIR) organic photodetectors (OPDs) are pivotal in numerous technological applications due to their excellent responsivity within the NIR region. Polyethylenimine ethoxylated (PEIE) has conventionally been employed as an electron transport layer (hole-blocking layer) to suppress dark current (JD) and enhance charge transport. However, the limitations of PEIE in chemical stability, processing conditions, environmental impact, and absorption range have spurred the development of alternative materials. In this study, we introduced a novel solution: a hybrid of sol-gel zinc oxide (ZnO) and N,N'-bis(N,N-dimethylpropan-1-amine oxide)perylene-3,4,9,10-tetracarboxylic diimide (PDINO) as the electron transport layer for NIR-OPDs. Our fabricated OPD exhibited significantly improved responsivity, reduced internal traps, and enhanced charge transfer efficiency. The detectivity, spanning from 400 to 1100 nm, surpassed ∼5 × 1012 Jones, reaching ∼1.1 × 1012 Jones at 1000 nm, accompanied by an increased responsivity of 0.47 A/W. Also, the unpackaged OPD remarkedly demonstrated stable JD and external quantum efficiency (EQE) over 1000 h under dark storage conditions. This innovative approach not only addresses the drawbacks of conventional PEIE-based OPDs but also offers promising avenues for the development of high-performance OPDs in the future.

Adsorbates Engineering on ZnO for Ultraviolet Light Activation–free Organic Photovoltaic Modules

Ultraviolet (UV) light is typically needed to activate inverted organic photovoltaic (OPV) devices with zinc oxide (ZnO) as electron transporting layer (ETL) for enhanced efficiency. Given that UV light may cause the degradation of active layers and interfaces, and considering the absence of UV light in typical indoor lighting, addressing the need of UV light activation for ZnO becomes paramount. Herein, we report the engineering of adsorbates on ZnO could solve this issue by increasing the annealing temperature and changing the recipe of ZnO. Increasing the content of O 1s at binding energy of 531 eV on ZnO in X‐ray photoelectron spectroscopy would be beneficial to alleviate the need of UV light activation. For the (ZnO)PEIE (zinc acetate dihydrate (ZAH) and polyethylenimine ethoxylated (PEIE) dissolved in 2‐methoxyethanol, PEIE used to provide amine in the precursor), annealing at 180 °C would eliminated S‐shape in the current density‐voltage (J‐V) characteristics without UV light activation. For traditional recipe of (ZnO)EA (ZAH and ethanolamine dissolved in 2‐methoxyethanol, ethanolamine used to provide amine in the precursor), annealing at 320 °C following by additional 0.1 wt% aqueous PEIE modification could reach the similar effect to the (ZnO)PEIE. OPV modules (9.8 cm2) with 180 °C annealed (ZnO)PEIE as ETL showed high photovoltaic performance under light conditions without UV: VOC = 4.73 V JSC = 16.3 μA/cm2, FF = 67.9% and PCE = 18.2% under LED (2700 K) condition at 1000 lux (light intensity of 288 μW/cm2); VOC = 5.76 V JSC = 2.8 mA/cm2, FF = 72.1% and PCE = 14.8% tested under 1 sun with the UV filter (light intensity of 0.788 sun). These high efficiencies were achieved in the modules without the need for UV light activation.This article is protected by copyright. All rights reserved.

Conductive Passivator and Dipole Layer Mixture Enabling High‐Performance Stable Perovskite Photoelectrode‐Based Solar Water Splitting

AbstractRecently, lead halide perovskites have attracted significant attention as promising absorber materials for photoelectrochemical (PEC) solar water splitting. However, charge‐accumulation‐induced ion migration at the interface causes perovskite degradation and efficiency loss. To suppress the charge accumulation and improve the PEC performance of the perovskite photoanode, a simple interface engineering is proposed by decorating the SnO2/perovskite interface with a mixture of polyethylenimine ethoxylated (PEIE) and chlorobenzenesulfonic acid (CBSA). The mixed CBSA+PEIE treatment effectively passivates the oxygen vacancies in SnO2 and adjusts the band alignment between SnO2 and the perovskite. The synergistic effects of the mixture treatment facilitate an effective carrier extraction at the SnO2/perovskite interface, enhance the PEC performance, and improve the stability of the device. The perovskite photoanode exhibits an impressive applied bias photon‐to‐current efficiency of 12.9% with an outstanding durability for 225 h. Furthermore, an unbiased solar water splitting is achieved using all the perovskite photoelectrodes, resulting in a remarkable unassisted solar‐to‐hydrogen efficiency of 10.9% and a continuous 22 h stable operation.

Solution-Processed ZnO with Conductivity over 1000 S cm-1 for ITO-Free Organic Photovoltaics.

Developing transparent conductors to replace indium tin oxide (ITO) is a critical objective in the field of organic optoelectronics. Non-atomically doped (NAD) ZnO thin films, while currently exhibiting limited conductivity, are highly promising candidates due to their unique advantages, such as having complete transparency in both the visible and near-infrared spectral regions, solution processability, and the desired surface electronic properties. In this work, the impact of surface modification by insulating polymers on the ultraviolet-enhanced conductivity of NAD-ZnO films is investigated. It was found that polymer modifiers that are rich in amino and hydroxyl groups are effective at increasing the concentration of oxygen vacancies and the conductivity of NAD-ZnO films. The highest conductivity of over 1000 S cm-1, which is more than twice as high as the previous record for NAD-ZnO films, is achieved using polyethylenimine ethoxylated (PEIE) to modify NAD-ZnO films. Subsequently, the replacement of ITO in organic photovoltaic devices by a ZnO/PEIE electrode is realized. The ZnO/PEIE-based OPV devices that were created exhibit performances comparable to those of ITO-based devices under simulated solar illumination and performances better than those achieved with ITO-based devices under simulated indoor illumination. These results make NAD-ZnO a promising candidate for the widespread replacement of ITO in optoelectronic devices.

Thienoisoindigo-Based Conjugated Polymers Synthesized by Direct Arylation Polycondensation.

A series of thienoisoindigo (TIG)-based conjugated polymers (CPs) with high molecular weights are synthesized by direct arylation polycondensation (DArP) by using TIG derivatives as CBr monomer and multi-halogenated thiophene derivatives, i.e., (E)-1,2-bis(3,4-difluorothien-2-yl)ethene (4FTVT), (E)-1,2-bis(3,4-dichlorothien-2-yl)ethene (4ClTVT), 3,3',4,4'-tetrafluoro-2,2'-bithiophene (4FBT), and 3,3',4,4'-tetrachloro-2,2'-bithiophene (4ClBT), as CH monomers. Density functional theory (DFT) calculations reveal the high selectivity between α-CH bonds in 4FTVT, 4ClTVT, 4FBT, and 4ClBT and β-CH bonds in TIG CBr monomer. All four resulting CPs exhibit low optical bandgaps of ca. 1.20eV and ambipolar transport characteristics with both electron and hole mobility above 0.1cm2 V-1 s-1 as elaborated with organic thin-film transistors (OTFTs). The polymer TIG-4FTVT delivers the best device performance. With this polymer, n-channel OTFTs with electron mobility up to 1.67cm2 V-1 s-1 and p-channel OTFTs with hole mobility up to 0.62cm2 V-1 s-1 are fabricated by modifying source/drain electrodes with polyethylenimine ethoxylated (PEIE) and MoO3 , respectively, to selectively inject electrons and holes.

Organic- inorganic nanoparticle composite as an electron injection/hole blocking layer in organic light emitting diodes for large area lighting applications

The charge carrier balance in organic light-emitting diodes (OLEDs) is crucial for optimizing external quantum efficiency (EQE). This is typically achieved by using charge injection and blocking layers deposited by vacuum deposition, which increases the fabrication time and cost. This study investigates the potential of polyethylenimine ethoxylated (PEIE), Zinc oxide (ZnO) nanoparticles and a PEIE-ZnO nanocomposite as functional layers for OLEDs with improved electron injection and hole blocking properties fabricated by solution processing. The PEIE-ZnO nanocomposite improves OLED performance: (a) a 28% increase in current density and enhanced electron mobility, (b) two times increase in electron mobility of the electron injection/transport layer, and (c) a reduction in surface and interface trap density. Consequently, the PEIE-ZnO nanocomposite shows an 84% increase in electroluminescence, 52.5% increase in luminous efficacy, 35.5% increment in external quantum efficiency, and increased stability as measured by degradation studies. Employing these interlayers fabricated by the novel and roll-to-roll compatible Spray-on-Screen deposition technique show a comparable OLED performance as that of spin coated and vacuum deposited electron injection layers, which makes the large area fabrication of optoelectronic devices with high efficiencies, high output, low cost, and long lifetime a possible reality.

Complementary Inverter Based on n‐Type and p‐Type OFETs with the Same Ambipolar Organic Semiconductor and ITO S/D Electrodes

AbstractBottom‐gate and bottom‐contact n‐type and p‐type organic field‐effect transistors (OFETs) are simultaneously obtained by combining the ambipolar semiconductor film of diketopyrrolopyrrole‐based conjugated polymer (P4FTVT‐C32) with indium tin oxide (ITO) source/drain (S/D) electrodes. P4FTVT‐C32 thin film exhibits n‐type unipolar property with the low work functional (WF) ITO S/D electrodes modified by polyethylenimine ethoxylated (PEIE) and it exhibits p‐type unipolar property with the high WF ITO S/D electrodes modified by HCl:InCl3. Hence, complementary inverters with transition voltages near VDD/2 and the maximum gain of 138 converting “1” state input into “0” state output are achieved by two different modifications via screen printing on ITO electrodes and then, only one‐time bar coating of P4FTVT‐C32. To further improve the performance and the uniformity of the OFET devices, the modification of octadecyltrichlorosilane (OTS) is also introduced. This work provides an easy‐handling method for the fabrication of low‐cost, high performance organic electronic devices and integrated circuits.

Nitrogenous Interlayers for ITO S/D Electrodes in N‐Type Organic Thin Film Transistors

AbstractThe commercialization of organic thin film transistors (OTFTs) is partly hindered by the high cost and stubborn work function (WF) of common Au source/drain (S/D) electrodes. In this work, indium tin oxide (ITO) S/D electrodes modified with three different nitrogenous interlayers including 1,4‐bis(2‐hydroxyethyl) piperazine (HEP), polyethylenimine ethoxylated (PEIE), and branched polyethylenimine (PEI) are adopted to fabricate n‐type OTFTs. The WF of bare ITO is 4.7 eV, whereas ITO modified with nitrogenous interlayers exhibits WFs ranging from 4.1 to 3.6 eV. By the first‐principle calculation and element analysis, the protonated amines are critical for the reduction of ITO surface WF. Besides, the interlayers with higher nitrogen contents are more likely to improve the wettability of octadecyltrichlorosilane (OTS) modified ITO substrates, and help to gain the continuous and oriented poly[2,5‐bis(4‐tetradecyloctadecyl)pyrrolo[3,4‐c]pyrrole‐1,4(2H,5H)‐dione‐alt‐5,5′‐di(thiophen‐2‐yl)‐2,2′‐(E)‐1,2‐bis(3,4‐difluorothien‐2‐yl)‐ethene] (P4FTVT‐C32) semiconductor thin films. Therefore, P4FTVT‐C32 based OTFTs with maximum electron field‐effect mobility of 1.95 cm2 V−1 s−1 are achieved by PEI treatments. These results indicate that the ITO S/D electrodes modified by nitrogenous interlayers can greatly slash costs and promote commercialization of OTFTs.

Passivating the Defects and Modulating the Surface Energy of ZnO Cathode Interlayer for Efficient Nonfullerene Organic Solar Cells

Charge transport is a meaningful process in nonfullerene organic solar cells (NOSCs). However, owing to the inherent defects of its metal oxide, the classic ZnO electron transport layer will severely hinder charge transport, and its high surface energy can cause a mismatch contact with the low surface energy active layer. Therefore, polyethylenimine ethoxylated (PEIE) is treated with quaternization and esterification to obtain polyethylenimine ethoxylated‐phenyl acetyl chloride (PEIE‐PAC). ZnO:PEIE‐PAC (ZnO‐P) with fewer defects and lower surface energy film is prepared by blending PEIE‐PAC with the precursor solution of ZnO. Compared with ZnO‐based control device with a power conversion efficiency (PCE) of 15.30%, the PCE of ZnO‐P‐based device is increased to 16.47% in PM6:Y6 system due to the optimization of oxygen defects and surface roughness. Meanwhile, owing to the decrease of surface energy in ZnO‐P, the contact between ZnO‐P and hydrophobic nonfullerene acceptors is closer, and it can isolate water and oxygen in the external environment, thus enhancing the stability in air of NOSCs. The ZnO‐P‐based PM6:Y6 device maintains long‐term storage stability in both N2 and ambient temperature, and after 1000 h aging, the PCE of ZnO‐P‐based device is still more than 85% of the initial PCE.

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.

Interfacial Dipole Layer Enables High-Performance Heterojunctions for Photoelectrochemical Water Splitting

TiO2 has been widely used as an n-type overlayer, simultaneously serving as a protective layer for photocathodes. However, the photovoltage generated from a TiO2 junction with p-type absorbers, such as p-Si, Sb2Se3, SnS, and Cu2O, is insufficient. We report a dipole reorientation strategy to overcome this limitation by inserting a polyethylenimine ethoxylated (PEIE) layer between a p-type absorber and TiO2. Furthermore, we demonstrate that the PEIE dipole orientation can be rearranged by increasing the layer thickness, leading to an upward shift of the TiO2 band edge. The magnitude of band shift induced by the dipole effect depends on the TiO2 layer thickness. Using this approach, the onset potential was significantly improved to 0.5 V versus the reversible hydrogen electrode (VRHE) in a p-Si/PEIE/TiO2/Pt device. The versatility of the effective dipole reorientation strategy was demonstrated by application to a range of TiO2-protected heterojunction photocathodes based on Sb2Se3, Cu2O, and SnS.

Work‐Function‐Tunable MXenes Electrodes to Optimize p‐CsCu2I3/n‐Ca2Nb3‐xTaxO10 Junction Photodetectors for Image Sensing and Logic Electronics

AbstractTunable work function has a high profile for the MXene‐based optoelectronic devices, and surface modification provides the huge potential to shift its Fermi level and modulate the work function. In this work, the window of MXene's work function is engineered from 4.55 to 5.25 eV by surface modification with LiF, Se, and polyethylenimine ethoxylated (PEIE). The vertical p‐CsCu2I3/n‐Ca2Nb3‐xTaxO10 junction photodetectors are constructed on the basis of the above surface‐modified MXenes, which changes the Schottky barrier between n‐Ca2Nb3‐xTaxO10 and the electrodes. In particular, the rectification effect is significantly enhanced by utilizing PEIE‐decorated MXene electrodes, resulting in a high rectification ratio of 16 136 and improved UV responsivity of 81.3 A W–1. Such high‐performance devices based on MXenes electrodes are compatible with the standard clean room fabrication process, realizing large‐scale flexible UV detectors that maintain 80% of the original current after 5000 times bending. Meanwhile, a photodetector array stimulated with UV of different wavelengths is constructed to reveal its potential for image sensing. Finally, functional “AND” and “OR” optoelectronic logic gates are developed for UV communication using Au/CsCu2I3/Ca2Nb3‐xTaxO10/MXene–PEIE photodetectors, enriching the application of MXene‐based optoelectronic devices. This work on tuning MXene work function via surface modification demonstrates that MXene is a promising candidate for future optoelectronics.

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.

Interface Engineering for All‐Inorganic CsPbIBr2 Perovskite Solar Cells with Enhanced Power Conversion Efficiency over 11%

Perovskite solar cells (PVSCs) receive great attention due to their excellent photovoltaic performance. Recently, all‐inorganic PVSCs have been extensively studied owing to their superior thermal and photo stability. Among them, CsPbIBr2 perovskite stands out due to its superb phase stability in ambient environment. However, the severe energy loss caused by non‐radiative recombination limits its development. Herein, a facile interface engineering method is employed to modify the electron transporting interface and reduce the energy loss. The insertion of a thin polyethylenimine ethoxylated (PEIE) film between SnO2 and the perovskite can simultaneously tune the work function of SnO2 and passivate the defects of the perovskite by the amino group in PEIE. Meanwhile, the PEIE interface serves as a modifier to enhance the crystallinity of the perovskite film, leading to enlarged grain size and reduced grain boundaries. As a result, the power conversion efficiency was enhanced from 8.7% for the SnO2‐based device to 11.2% for the SnO2/PEIE‐based device, with an open‐circuit voltage of 1.29 V, a short‐circuit current of 11.0 mA/cm2, and a fill factor of 78.6%. Moreover, the photostability of devices were improved, which retained over 80% of its initial efficiency under continuous one sun illumination for 500 h. This work proves the effectiveness of interface engineering to boost the efficiency and stability of all‐inorganic PVSCs.

Design of All-Fused-Ring Electron Acceptors with High Thermal, Chemical, and Photochemical Stability for Organic Photovoltaics

High-performance donor–acceptor electron acceptors containing 2-(3-oxo-2,3-dihydro-1H-inden-1-ylidene)malononitrile (INCN)-type terminals are labile toward photooxidation and basic conditions, and ...

Critical role of additive-induced molecular interaction on the operational stability of perovskite light-emitting diodes

Summary Despite rapid improvements in efficiency and brightness of perovskite light-emitting diodes (PeLEDs), the poor operational stability remains a critical challenge hindering their practical applications. Here, we demonstrate greatly improved operational stability of high-efficiency PeLEDs, enabled by incorporating dicarboxylic acids into the precursor for perovskite depositions. We reveal that the dicarboxylic acids efficiently eliminate reactive organic ingredients in perovskite emissive layers through an in situ amidation process, which is catalyzed by the alkaline zinc oxide substrate. The formed stable amides prohibit detrimental reactions between the perovskites and the charge injection layer underneath, stabilizing the perovskites and the interfacial contacts and ensuring the excellent operational stability of the resulting PeLEDs. Through rationally optimizing the amidation reaction in the perovskite emissive layers, we achieve efficient PeLEDs with a peak external quantum efficiency of 18.6% and a long half-life time of 682 h at 20 mA cm−2, presenting an important breakthrough in PeLEDs.

One-step solution-processed low surface roughness silver nanowire composite transparent electrode for efficient flexible indium tin oxide-free polymer solar cells

We present a kind of all-solution-processed transparent electrode comprising of the mixture of silver nanowires (AgNWs) and ZnO nanoparticles modified with polyethylenimine ethoxylated (PEIE) solution by one-step doctor-blade-coating (DBC) processing. The AgNWs-ZnO-PEIE (AZP) composite films prepared with DBC exhibit highly transparent and conductive properties as well as low surface roughness. The optimized AZP film is highly transparent in the wavelength range of 350-1000 nm and the sheet resistance can be as low as 22-25 Ω/square with transmittance over 91% at 550 nm. A small content of PEIE can effectively prevent two kinds of nano components, AgNWs and ZnO nanoparticles, from agglomeration in solution and aggregation during solution processing, and therefore results in a very smooth and transparent AZP film without sacrificing its conductivity. Since the AgNWs are well embedded within the electron-transporting ZnO matrix, the prepared AZP film can serve as a dual function of both the transparent electrode and electron-transporting layer. The flexible PSCs based on the one-step prepared AZP electrode without an electron-transporting layer attained a power conversion efficiency (PCE) of 8.31%. A comparison study on the commercial indium tin oxide (ITO)/polyethylene terephthalate (PET) and AZP/PET-based flexible PSCs with the same device structure shows quite similar PCE (9.14% and 8.94%), but the polymer solar cells fabricated on the AZP/PET substrate show more excellent flexibility than the ITO/PET-based PSCs.