Polyethylenimine Ethoxylated Research Articles

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.

Polyethylenimine-Ethoxylated Interfacial Layer for Efficient Electron Collection in SnO2-Based Inverted Organic Solar Cells

In this work, we studied inverted organic solar cells based on bulk heterojunction using poly(3-hexylthiophene-2,5-diyl):[6,6]-phenyl-C71-butyric acid methyl ester (P3HT:PCBM) as an active layer and a novel cathode buffer bilayer consisting of tin dioxide (SnO2) combined with polyethylenimine-ethoxylated (PEIE) to overcome the limitations of the single cathode buffer layer. The combination of SnO2 with PEIE is a promising approach that improves the charge carrier collection and reduces the recombination. The efficient device, which is prepared with a cathode buffer bilayer of 20 nm SnO2 combined with 10 nm PEIE, achieved Jsc = 7.86 mA/cm2, Voc = 574 mV and PCE = 2.84%. The obtained results exceed the performances of reference solar cell using only a single cathode layer of either SnO2 or PEIE.

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.

Highly crystalline two-dimensional copolymer with dominant face-on orientation for high performance polymer solar cells

We designed and synthesized a novel series of two-dimensional (2D) conjugated polymers (P1-2T, P2-2T2F and P3-4T2F) containing 2,2′-bithiophene (2T) and 3,3′-difluoro-2,2′-bithiophene (2T2F) as donor units, and 4,7-benzo[c][1,2,5]thiadiazole (BT) and 4,7-di(thiophen-2-yl)benzo[c][1,2,5]thiadiazole (DTBT) as acceptor units appended with conjugated vinyl-terthiophene (VTT) side chain. We comprehensively investigated the effect of fluorination and thiophene (T) π-spacer on the optoelectronic properties and photovoltaic performance of the resulting copolymers. In comparison with non-fluorinated polymer P1-2T, the fluorinated polymer P2-2T2F and P3-4T2F had down shifted highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energy levels with an enhanced absorption band. Moreover, 2D grazing incidence wide-angle X-ray scattering and space charge limited current measurement showed that the presence of thiophene π-spacer in P3-4T2F promoted dominant face-on orientation, high crystallinity and enhanced hole mobility, compared with P2-2T2F. As a result, the inverted polymer solar cell based on the P3-4T2F:PC61BM blend exhibited a high power conversion efficiency (PCE) of 6.66% with a Jsc of 12.99 ± 0.30 mA/cm−2. In contrast, the P1-2T:PC61BM and P2-2T2F:PC61BM devices without π-spacer showed a PCE of 2.22% and 0.95%, respectively. The PCE of the P3-4T2F:PC61BM device was further improved to 6.89% by using a polyethylenimine ethoxylated (PEIE) interlayer between ITO and ZnO. This study reinvigorates the key modulation of a 2D conjugated polymer with improved photovoltaic performance.

Improving electron transport by using a NaCl/polyethylenimine ethoxylated double layer for high-efficiency polymer solar cells

This work presents the combination of NaCl and polyethylenimine ethoxylated (PEIE) as a double-layer electron transport layer (ETL, NaCl/PEIE) to enhance the capacity of electron transport. The polymer solar cell based on poly(3-hexylthiophene):phenyl C61-butenoic acid methyl ester achieves a high power conversion efficiency (PCE) of 3.83% by using a NaCl/PEIE bilayer as an ETL; moreover, its PCE is increased by 15% compared with the PCE of the pure PEIE device. Electrochemical impedance and conductivity measurements indicate that the performance of the device with the NaCl/PEIE double layer is enhanced because of its low interfacial contact resistance and fast charge transfer capability.

Role of CdSe and CdSe@ZnS quantum dots interlayers conjugated in inverted polymer solar cells

We demonstrate the use of CdSe quantum dots (QDs) as an interlayer for improving photovoltaic performance in the inverted polymer solar cells (iPSCs). The conjugation of CdSe and [email protected] [email protected] QDs between polyethylenimine ethoxylated (PEIE) polymer and PTB7:PC71BM blended layer played an important role in increasing the short circuit current density by Förster resonance energy transfer (FRET) and efficient charge transport. The drastic mutual photoluminescence quenching suggests that the photon energy absorbed by PTB7:PC71BM are effectively transferred to the QDs. The PTB7:PC71BM based iPSCs with the CdSe QDs interlayer exhibits higher power conversion efficiency of 8.13%, which is 13.4% higher than that of the control device. The iPSCs with [email protected] QDs interlayer showed relatively lower PCE of 7.31%, which could be due to an increase in carrier recombination inside QDs by relatively high energy level of ZnS shell. As a consequence, the enhanced photovoltaic performance of iPSCs with CdSe QDs interlayer can be attributed to an effective charge transport and an increase in the overall photocurrent by FRET.

Improvement in hole transporting ability and device performance of quantum dot light emitting diodes.

In this research, we demonstrate a novel approach to improve the device performance of quantum dot light emitting diodes (QLEDs) by blending an additive BYK-P105 with poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) as the hole transport layer. In addition, for the first time, polyethylenimine ethoxylated (PEIE)-modified zinc oxide nanoparticles (ZnO NPs) as the electron transport layer were applied in regular-type QLEDs for achieving high device efficiency. A very high brightness of 139 909 cd m−2 and current efficiency of 27.2 cd A−1 were obtained for the optimized device with the configuration of ITO/PEDOT:PSS + BYK-P105/PVK/CdSe QDs/ZnO NPs/PEIE/LiF/Al that shows promising use in light-emitting applications.

Characteristics of electron injection at the oxide electrode/polyethylenimine ethoxylated/Alq3 interface

Inverted organic light-emitting diodes (inverted OLEDs) require electron injection to an organic semiconductor from a transparent oxide electrode. Polyethylenimine ethoxylated (PEIE) has attracted considerable attention as an electron injection material. An injection mechanism has been suggested; however, the barrier height of electron injection has not been determined. In this paper, we present the experimental values for the electron injection barrier height at the transparent oxide electrode/PEIE/organic semiconductor interface. Electron-only devices, consisting of indium-tin-oxide (ITO)/PEIE/tris(8-hydroxyquinolinato) aluminum (Alq3)/Al, are fabricated. The temperature dependence of the current–voltage curves is measured corresponding to the electron injection of the ITO/PEIE/Alq3 interface. The current–voltage curves are found to be independent of the measurement temperature, which is explained by the tunneling model. The tunneling injection barriers height are calculated, and the experimental injection barrier height will be important for the development of inverted OLED devices.

Enhanced Nucleation of Atomic Layer Deposited Contacts Improves Operational Stability of Perovskite Solar Cells in Air

AbstractMetal‐halide perovskites show promise as highly efficient solar cells, light‐emitting diodes, and other optoelectronic devices. Ensuring long‐term stability is now a major priority. In this study, an ultrathin (2 nm) layer of polyethylenimine ethoxylated (PEIE) is used to functionalize the surface of C60 for the subsequent deposition of atomic layer deposition (ALD) SnO2, a commonly used electron contact bilayer for p–i–n devices. The enhanced nucleation results in a more continuous initial ALD SnO2 layer that exhibits superior barrier properties, protecting Cs0.25FA0.75Pb(Br0.20I0.80)3 films upon direct exposure to high temperatures (200 °C) and water. This surface modification with PEIE translates to more stable solar cells under aggressive testing conditions in air at 60 °C under illumination. This type of “built‐in” barrier layer mitigates degradation pathways not addressed by external encapsulation, such as internal halide or metal diffusion, while maintaining high device efficiency up to 18.5%. This nucleation strategy is also extended to ALD VOx films, demonstrating its potential to be broadly applied to other metal oxide contacts and device architectures.

Small energy loss and high open circuit voltage in conventional structure polymer solar cells with the mixture thin films of polyethylenimine ethoxylated and TiOX as the electron extraction layer and Ag as the cathode

One of the challenges facing the fabrication of high-performance conventional structure polymer solar cells (PSCs) is the development of new interface materials that have better air stability and charge carrier collection and transport ability. In this study, the mixture thin films of polyethylenimine ethoxylated (PEIE) and TiOX are developed as the electron extraction layer (EEL) and Ag as the cathode for the application in PSCs, replacing the Ca/Al composite cathode. Ultraviolet photoelectron spectroscopy (UPS) and space-charge-limited current (SCLC) measurements demonstrate that PEIE:TiOX/Ag shows appropriate energy levels, substantially reduced barrier potential, weakened charge carrier recombination and enhanced electron mobility. As a result, the PEIE:TiOX-based PSCs demonstrate not only an enhanced power conversion efficiency (PCE) of 10.94% but also the photovoltaic performance insensitive to the storage time, yielding an aged PCE that is 92% of the fresh PCE. This result can be further explained by the dependence of the charge carrier mobility on storage time. Our work suggests exploiting the PEIE:TiOX/Ag composite thin films as the composite cathode replacing Ca/Al thin films for successfully enhancing the photovoltaic performance and improving the stability of PSCs.

Doping of Tetraalkylammonium Salts in Polyethylenimine Ethoxylated for Efficient Electron Injection Layers in Solution-Processed Organic Light-Emitting Devices

For efficient electron injection, a method to control the work functions (WFs) of ZnO electrodes in organic light-emitting devices (OLEDs) is reported in this study. First, ZnO was modified by doping of tetraalkylammonium salts (TRAX) into polyethylenimine ethoxylated (PEIE) for the WF control. Tetrabutylammonium salts (TBAX), where X = chloride, bromide, iodide, acetate, thiocyanate, and tetrafluoroborate anions, were doped into PEIE. A WF of nondoped PEIE-modified ZnO was 3.65 eV, whereas TBAX-doped PEIE-modified ZnO exhibited WFs ranging from 3.52 to 3.00 eV depending on the anion. TBAX salts exhibited different electron-donating capabilities depending on the anion, and the doping of TBAX with a large electron-donating capability exhibited a large WF reduction effect. In addition, tetraethyl- and tetrahexylammonium chlorides were doped into PEIE. PEIE doped with TRACl containing long alkyl chains exhibited a large WF reduction effect due to its low electron-accepting capabilities. In addition, the WF reduction mechanism was considered by the depth direction analysis of the PEIE:TBAX films. Finally, the ZnO/PEIE:TRAX bilayers were applied as electron injection layers in poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] emissive-layer-based OLEDs with an inverted structure. The ZnO/PEIE:TBAX devices with low WFs exhibited low driving voltages.

The modified PEDOT:PSS as cathode interfacial layer for scalable organic solar cells

Abstract Poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) is extensively used as an anode interfacial layer in optoelectronic devices due to its excellent hole-transporting properties and high work function (ϕF). In this study, we propose a simple and cost-effective method to controllably tune the ϕF of PEDOT:PSS from 5.1 eV to 3.95 eV by doping the polyethylenimine ethoxylated (PEIE). The PEIE-doped PEDOT:PSS films can function as a cathode interfacial layer in organic solar cells, showing the comparable performance to a conventional ZnO-based cell. The photoelectric characteristics, surface morphology, and electron transport ability of PEIE-doped PEDOT:PSS films were systematically investigated to elucidate the physical nature of the conversion from hole transport to electron transport. This strategy provides an effective charge transport layer for optoelectronic devices, which is suitable for large-scale, industrial applications.

Thin metal top electrode and interface engineering for efficient and air-stable semitransparent perovskite solar cells

To find promising device architecture for air-stable as well as efficient semitransparent perovskite solar cells (PeSCs), Ag & Cu semitransparent top electrode and interfacial engineering technologies are explored in PeSCs consisting with indium tin oxide (ITO)/hole transporting layer (HTL)/CH3NH3PbI3/[6,6]-phenyl-C61 butyric acid methyl ester (PCBM)/Ag or Cu. Devices with NiOx HTL exhibits better performance than conventional poly (3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) based devices and modification of PCBM with polyethylenimine ethoxylated (PEIE) also induces improved performance. Optimized semitransparent PeSC with Cu shows superior performance, achieving a power conversion efficiency (PCE) of 11.95% and average visible transmittance (AVT) of ∼20%, and stability to Ag based device.

Amine-Based Interfacial Engineering in Solution-Processed Organic and Perovskite Solar Cells.

Solution-processed organic solar cells (OSCs) and hybrid perovskite solar cells (PvSCs) generally require appropriate transparent electrode with a low work function, which improves the electron extraction, increases the built-in potential, and suppresses charge recombinations. Hence, interfacial modifiers between the cathode and the photoactive layer play a significant role in OSCs and PvSCs, as they provide suitable energy-level alignment, leading to desirable charge carrier selectivity and suppressing charge carrier recombinations at the interfaces. Here, we present a comprehensive study of the energy-level mapping between a transparent electrode and photoactive layers to enhance the electron-transport ability by introducing amine-based interfacial modifiers (ABIMs). Among the ABIMs, polyethylenimine ethoxylated (PEIE) incorporating inverted OSCs shows enhanced power conversion efficiencies (PCEs) from 0.32 to 9.83% due to large interfacial dipole moments, leading to a well-aligned energy level between the cathode and the photoactive layer. Furthermore, we explore the versatility of the PEIE ABIM by employing different photoactive layers with fullerene derivatives, a nonfullerene acceptor, and a perovskite layer. Promisingly, inverted nonfullerene OSCs and planar n-i-p PvSCs with PEIE ABIM show outstanding PCEs of 11.88 and 17.15%, respectively.

Indium Tin Oxide–Based Fully Spray‐Coated Inverted Solar Cells with Nontoxic Solvents: The Role of Buffer Layer Interface on Low‐Bandgap Photoactive Layer Performance

In bulk heterojunction solar cells, the morphology of the interfaces between the photoactive layer (PAL) and charge transporting layers during the deposition process plays a key role in achieving high‐efficiency devices. Herein, an inverted fully spray‐coated solar cell fabricated on an indium tin oxide (ITO)‐glass substrate is presented. It is demonstrated that a spray‐coated double electron transporting layer composed of zinc oxide (ZnO) nanoparticles coated with polyethylenimine ethoxylated (PEIE) improves the morphology of the spray‐coated active layer on top of the spray‐coated cathode. Moreover, focusing on the hole transporting layer and anode, the performance obtained using a commercial poly(3,4‐ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) blend is compared with a high‐conductive anhydrous PEDOT:PSS (A‐PEDOT) mixed with a commercial PEDOT:PSS (CPP‐105D) as transporting layer. By optimizing the spray deposition of all the layers, a fully scalable spray process is used to produce polymer solar cells with ITO/ZnO/PEIE/poly[[4,8‐bis[(2‐ethylhexyl)oxy]benzo[1,2‐b:4,5‐b’]dithiophene‐2,6‐diyl] [3‐fluoro‐2‐ [(2‐ethylhexyl)carbonyl] thieno[3,4‐b]thiophenediyl]] (PTB7): [6,6]‐phenyl‐C70‐butyric‐acid‐methyl‐ester (PC70BM)/CPP:A‐PEDOT structure, achieving a power conversion efficiency (PCE) of 3.6%. Such result is significant if compared to a spray‐coated structure with evaporated anode (MoO3‐Ag). In this case (ITO/ZnO/PEIE/PTB7:PCBM/MoO3‐Ag), a power conversion efficiency of 5.5% is obtained.

Roles of Polyethylenimine Ethoxylated in Efficiently Tuning the Thermoelectric Performance of Poly(3,4-ethylenedioxythiophene)-Rich Nanocrystal Films.

The regulation of oxidation levels is of great importance as an efficient way to optimize the thermoelectric (TE) performance of conducting polymers. Many efforts have been devoted to the acquisition of a high TE performance for poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) by oxidation/reduction post treatment to achieve an effective compromise. However, a strong oxidant/reductant is usually employed to tune the TE performance of PEDOT:PSS with high electrical conductivity (σ) and Seebeck coefficient ( S), and it also presents a number of operational challenges depending on a fast reaction rate. Herein, nontoxic polyethylenimine ethoxylated (PEIE) served as a reductant to successfully realize an enhanced S for PEDOT:PSS, besides playing a significant anion-blocking role in enabling the efficient modulation of the oxidation level by sulfuric acid (H2SO4) with a longer operating time. Eventually, a good PEDOT-rich nanocrystal is achieved by a sequential dipping process in PEIE/ethylene glycol and H2SO4 solutions. The large TE power factor of 133 μW m-1 K-2 can be ascribed to the good formation of PEDOT-rich nanocrystals and an effective compromise between σ and S of PEDOT:PSS films. A mechanism was elucidated for the efficient regulation of σ and S enabling high performance of organic TE materials.

12.5% Flexible Nonfullerene Solar Cells by Passivating the Chemical Interaction Between the Active Layer and Polymer Interfacial Layer

Nonfullerene (NF) organic solar cells (OSCs) have been attracting significant attention in the past several years. It is still challenging to achieve high-performance flexible NF OSCs. NF acceptors are chemically reactive and tend to react with the low-temperature-processed low-work-function (low-WF) interfacial layers, such as polyethylenimine ethoxylated (PEIE), which leads to the "S" shape in the current-density characteristics of the cells. In this work, the chemical interaction between the NF active layer and the polymer interfacial layer of PEIE is deactivated by increasing its protonation. The PEIE processed from aqueous solution shows more protonated N+ than that processed from isopropyl alcohol solution, observed from X-ray photoelectron spectroscopy. NF solar cells (active layer: PCE-10:IEICO-4F) with the protonated PEIE interfacial layer show an efficiency of 13.2%, which is higher than the reference cells with a ZnO interlayer (12.6%). More importantly, the protonated PEIE interfacial layer processed from aqueous solution does not require a further thermal annealing treatment (only processing at room temperature). The room-temperature processing and effective WF reduction enable the demonstration of high-performance (12.5%) flexible NF OSCs.

Efficient CuInS2/ZnS Quantum Dots Light‐Emitting Diodes in Deep Red Region Using PEIE Modified ZnO Electron Transport Layer

In this study, the enhanced device performance of CuInS2/ZnS quantum dots‐based light‐emitting didoes (QLEDs) for photomedical applications using polyethylenimine ethoxylated (PEIE)‐modified ZnO as electron transport layer has been reported. The device enhancement is investigated by applying time‐resolved photoluminescence and transient electroluminescence spectra. The results show that the modification of PEIE on ZnO layer limits the electron injection into quantum dots layer and reduces the accumulation of electrons at ZnO/QD interface. This provides an effective way to suppress the charging processes of quantum dots and thus enhance the device efficiency. As a result, the synergistic effect of PEIE modifying layer leads to a record current efficiency of 2.75 cd A−1 for the CuInS2/ZnS‐based QLEDs with deep red emission at 650 nm.

Improved Performance of Quantum‐Dot Photodetectors Using Cheap and Environmentally Friendly Polyethylene Glycol

AbstractColloidal quantum dot (CQD) photodetectors (PDs) are developed. The on/off current ratio is improved by applying organic cathode buffer layers (CBLs), such as polyethylenimine ethoxylated (PEIE) and polyethylene glycol (PEG). The on‐current of CQD‐PDs (QPDs) is increased by the decreased work function of ZnO/CBLs via forming a permanent dipole moment at the interface of ZnO and CBLs. The off‐current is significantly decreased by the improved interfacial morphology via softening the ZnO surfaces. In the photoconductive mode for the fast response time of a signal, PEG‐ and PEIE‐treated QPDs exhibit improved photodetecting properties. Notably, the performance of PEG‐treated QPDs fluctuates less at the concentration of the prepared CBL solution. The utilization of environmentally friendly and cheap PEG as CBLs is attractive for QPDs. The organic CBL is highly effective for QPDs to improve both on‐ and off‐current characteristics.

High fill factor over 82% enabled by a biguanide doping electron transporting layer in planar perovskite solar cells

N-type doping in electron transport materials is an effective way to improve the electron collection and enhance the performance of the perovskite solar cells (PSCs). Here, for the first time, an antibiotic and antimicrobial compound of 1-(o-Tolyl) biguanide (oTb) is used to dope the electron transport material of phenyl-C61-butyric acid methyl ester (PCBM). The oTb doping into the PCBM can increase the conductivity and reduce the work function of the PCBM. The oTb doping can significantly enhance the fill factor (FF) of the perovskite solar cells with the structure of glass/ITO/NiOx/MAPbI3/(oTb)PCBM/(PEIE)/Ag. For the cells without PEIE (polyethylenimine ethoxylated) coating, the oTb doping increases the FF from 0.57 to 0.73. S-shaped of the current density-voltage (J-V) characteristic under illumination is removed after the oTb doping. For the cells with PEIE coating between the (oTb)PCBM and Ag, the oTb doping increases the FF from 0.70 to 0.82. These results show the potential of the oTb as an n-dopant in the applications of perovskite solar cells.