Simple Device Architecture Research Articles

Natural Organic Pectin Polysaccharide Based Resistive Random Access Memory

Nowadays, non-volatile memory technologies have been widely applied in different areas. Of these memory technologies, non-volatile resistive random access memory (ReRAM) is attractive because of its simple device architecture and fabrication process, high scalability and data density, good performances in terms of switching speed, high power efficiency and reasonably wide memory window. In order to address the issues of disposable and degradation of electronic waste by typical ReRAM with the active layer made of inorganic oxide materials and fossil-fuel based polymeric materials, a green and sustainable strategy has been adopted in producing ReRAM by using natural organic-based materials based on protein and carbohydrate, such as honey, fructose, aloe vera, etc. Among these materials, pectin-polysaccharide thin film has demonstrated promising resistive switching characteristics. The two ranges of pectin concentrations that have been investigated are ³5 mg/ml and £1.5 mg/ml, and it showed that pectin with concentration <1.5 mg/ml reveals a higher ON/OFF ratio. However, the resistive switching characteristics with pectin concentration between 1.5 mg/ml and 5 mg/ml have yet been explored and reported. In this work, pectin with concentrations of 1.5~5 mg/ml were prepared from pectin-polysaccharide solution into the active switching layer, and ReRAM devices with such pectin resistive switching layer were fabricated. The pectin-polysaccharide solution, pectin resistive film, and ReRAM devices were systematically investigated. Surface tension and contact angle of pectin-polysaccharide precursor solutions as a function of pectin concentration on the substrate were measured by a goniometer. Surface topography of solidified thin films was characterized by an atomic force microscope (AFM) and a field-emission scanning electron microscope (FE-SEM). Chemical functional groups of the pectin-polysaccharide precursor solutions and solidified thin films were examined by a Fourier transform infrared (FTIR) spectroscopy. The resistive switching behaviors were characterized and compared by electrical measurement. The results show that 4 mg/ml recorded the highest ON/OFF ratio compared to ever reported values, as well as desirable memory window, non-volatility in retention, and stability over 100 cycles. This study proves that pectin-polysaccharide is a promising green and sustainable bio-organic material for non-volatile ReRAM for electronic applications such as in emerging neuromorphic computing systems.

Metamaterial-inspired infrared electrochromic devices with wideband microwave absorption for multispectral camouflage

Infrared (IR) electrochromic devices, capable of dynamically controlling thermal radiation, hold promising applications in adaptive camouflage. However, the strong microwave reflective properties inherent in the device’s electrodes present a significant challenge, rendering them susceptible to radar detection and weakening their camouflage effect. Inspired by the remarkable electromagnetic control capabilities of metamaterials, the integration of frequency selective surfaces into IR electrochromic devices is proposed to address this multispectral compatibility challenge. The designed integrated metadevices simultaneously exhibit large and reversible IR emissivity tunability (Δε≥0.55 at 3–5 μm, Δε≥0.5 at 7.5–13 μm) and wideband microwave absorption (reflection loss ≤−10 dB at 8.5–18 GHz). Furthermore, the monolithic integrated design of the shared barium fluoride substrate offers a simple device architecture, while careful design considerations mitigate coupling between IR electrochromism and microwave wideband absorption. This work introduces opportunities for the development of multispectral adaptive camouflage systems, offering potential advancements in concealment technology.

The population growth model of electrostatic charges: A novel concept for engineering optimal performance triboelectric nanogenerators

Lateral sliding triboelectric nanogenerators LS-TENGs promise to combine low cost and high-efficiency mechanical energy harvesting at low frequency with the advantages of light weight and simple device architecture. To date, device power generation optimization has only been addressed on the framework of the optimal load resistance through the maximum power transfer theorem (MPTT). However, MPTT is a concept to optimize the power transferred from TENGs to loads, but not for optimizing the power generated by the TENG itself. In response, this work reports a concept that resembles the population growth model of species for designing enhanced performance LS-TENGs with optimal charge-generating rate. In this way, devices designed under the proposed concept possess a significantly enhanced optimal charge and power generation rate up to 3-fold and 8-fold respectively superior to those found for conventional rectangular TENGs with similar capacity, which allows us power up sustainably for hours low power consumption devices with a few minutes of mechanical energy harvesting. Thereby, this model aids in the development of enhanced performance LS-TENGs capable of collecting mechanical vibrations and optimally converting them into electrical energy by breaking the limits set by the MPTT, as well as opening a route towards batteryless power autonomy.

Flexible Organic Electrochemical Transistor Based on Conjugated Conducting Polymers

— The use of organic electrochemical transistors (OECTs) based on conjugated polymers has gained significant recognition owing to their impressive performance, flexibility, ease of fabrication, and suitability for specific applications where solid-state transistors may not be efficiently employed. Key advantages of OECT technology, such as simple device architecture, robustness in ambient or aqueous environments, straightforward additive manufacturing processes, low operational voltage, and compatibility with flexible, rough, stretchable, and large-area substrates, underscore its significance in various applications. These applications span the sensing of glucose [1], bacteria [2], dopamine [3], DNA [4], lactate [5], cell activities [6], and electrophysiological signals [7]. Notably, the absence of the necessity for a reference electrode, a crucial feature for wearable and textile sensors compared to three electrode-based electrochemical sensors, stands out. In this context, we have fabricated a side-gated OECT on a flexible polyethylene terephthalate (PET) substrate through a scalable screen-printing process where the source, drain, and gate terminals are screen-printed using silver (Ag) conductive ink. The semiconducting channel material employed is polyethylene dioxythiophene: polystyrene sulfonate (PEDOT: PSS), which is spin-coated. Additionally, poly methyl methacrylate (PMMA) has been spin-coated to serve as the dielectric. The OECT operates by volumetric gating of the channel through a gel electrolyte containing poly sodium 4-styrene sulfonate (PSSna), enabling polarization of the gate and channel to induce charge accumulation or depletion, driven by the application of a gate-source voltage. The OECT device structure demonstrated switching from the "ON" to "OFF” state with the application of a positive gate voltage, indicating its functionality as a p-type depletion mode transistor. Additionally, the OECT displayed a transconductance (gm) of 6.25×10-4 A/V, mobility (µ) of 1.242×1010 cm2 /Vs, and a threshold voltage (Vth) of -0.39 V, with the on/off ratio being relatively low at 7.22. The repeatability was confirmed through the fabrication of three devices that exhibited nearly identical behavior. Furthermore, in pursuit of faster response time, lower operating voltage, and miniaturization, additional work involves downscaling the active area length to 100µm from the reported 4mm active area length. The fabrication method not only holds the capability for large-scale production with a high yield in a cost-effective manner but also opens up possibilities for applications requiring swift design changes and digitally enabled direct-write techniques. Future work emphasizes functionalizing the electrolyte used in OECT to detect biomolecules such as glucose, pH, and ion species. Thus, this research underscores the potential usability of fabricated OECTs in various high-performance chemical and biological sensing applications. REFERENCES Tang, H.; Yan, F.; Lin, P.; Xu, J.; Chan, H.L.W. Highly Sensitive Glucose Biosensors Based on OrganicElectrochemical Transistors Using Platinum Gate Electrodes Modified with Enzyme and Nanomaterials.Adv. Funct. Mater. 2011, 21, 2264–2272. [CrossRef]He, R.-X.; Zhang, M.; Tan, F.; Leung, P.H.M.; Zhao, X.-Z.; Chan, H.L.W.; Yang, M.; Yan, F. Detection of bacteria with organic electrochemical transistors. J. Mater. Chem. 2012, 22, 22072–22076. [CrossRef]Gualandi, I.; Tonelli, D.; Mariani, F.; Scavetta, E.; Marzocchi, M.; Fraboni, B. Selective detection of dopamine with an all PEDOT:PSS Organic Electrochemical Transistor. Sci. Rep. 2016, 6, 35419. [CrossRef]Tao, W.; Lin, P.; Hu, J.; Ke, S.; Song, J.; Zeng, X. A sensitive DNA sensor based on an organic electrochemical transistor using a peptide nucleic acid-modified nanoporous gold gate electrode. RSC Adv. 2017, 7, 52118–52124. [CrossRef]Braendlein, M.; Pappa, A.-M.; Ferro, M.; Lopresti, A.; Acquaviva, C.; Mamessier, E.; Malliaras, G.G. Owens, R.M. Lactate Detection in Tumor Cell Cultures Using Organic Transistor Circuits. Adv. Mater. 2017, 1605744.Lin, P.; Yan, F.; Yu, J.; Chan, H.L.W.; Yang, M. The Application of Organic Electrochemical Transistors in Cell-Based Biosensors. Adv. Mater. 2010, 22, 3655–3660Liang, Y.; Ernst, M.; Brings, F.; Kireev, D.; Maybeck, V.; Offenhäusser, A.; Mayer, D. High Performance Flexible Organic Electrochemical Transistors for Monitoring Cardiac Action Potential. Adv. Healthc. Mater. 2018, 1800304. [CrossRef] Figure 1

Efficient white light-emitting electrochemical cells based on quantum-dot color conversion layers with high EQE >20 %

Solid-state light-emitting electrochemical cells (LECs) offer promising benefits, including simple device architecture, low operating voltage, and insensitivity to electrode work functions. These advantages make them highly suitable for low-cost display and lighting applications, with significant potential for widespread adoption. However, great challenges remain in realizing stable and efficient white LECs. In this work, the blue LECs integrated with red or yellow/red quantum-dot (QD) color conversion layers (CCLs) are shown to achieve efficient and stable white emissions. When the blue LECs are combined with red QD CCLs, they achieve an external quantum efficiency (EQE) exceeding 20 % at a low current density of 0.003 mA cm−2. Alternatively, the blue LECs integrated with yellow/red QD CCLs deliver white emissions with a low CCT <2500 K and a high CRI up to 93 while the peak EQE at a low current density of 0.005 mA cm−2 still remains high (>16 %). The data effectively showcase that efficient and stable white emission can be achieved through partial energy down-conversion from the blue LECs to the QD CCLs, and the proposed white light sources are potential candidates for lighting applications.

Ambipolar Charge Injection and Bright Light Emission in Hybrid Oxide/Polymer Transistors Doped with Poly(9‐Vinylcarbazole) Based Polyelectrolytes

AbstractLight‐emitting transistors (LETs) are a remarkable, emerging class of electronic devices that combine the switching function of field‐effect transistors (FETs) and the light‐emitting function of light‐emitting diodes (LEDs). In order to achieve efficient light emission, effective electron and hole injection from source and drain electrodes is necessary. Various strategies have been introduced to accomplish this, such as incorporating asymmetric electrodes or charge injection layers during device fabrication. These approaches have inevitably introduced complexity in the device fabrication process. Herein, light‐emitting electrochemical transistors (LECTs) are demonstrated that combine principles of electrochemistry and optoelectronics to achieve multi‐functionality in a simple device architecture. Hybrid polyelectrolytes, poly(9‐vinylcarbazolesulfonate)‐ lithium and copper (II) salts (PVK‐Li and PVK‐Cu) incorporating Li+ ion and Cu2+ ions are added at variable concentrations to the organic emitting layer of LECTs to effect electrochemical p‐type doping. This electrochemical doping approach yielded improvements in electrical and optical performances including mobilities, brightnesses, and external quantum efficiency of the LECTs. The dynamics of how charges including ions, electrons, and holes move and interact are discussed in the device to facilitate emissive charge carrier recombination and light emission. This investigation provides valuable insights into the realms of both electrochemistry and optoelectronics.

High-Performance All-Inorganic Architecture Perovskite Light-Emitting Diodes Based on Tens-of-Nanometers-Sized CsPbBr3 Emitters in a Carrier-Confined Heterostructure.

Developing green perovskite light-emitting diodes (PeLEDs) with a high external quantum efficiency (EQE) and low efficiency roll-off at high brightness remains a critical challenge. Nanostructured emitter-based devices have shown high efficiency but restricted ascending luminance at high current densities, while devices based on large-sized crystals exhibit low efficiency roll-off but face great challenges to high efficiency. Herein, we develop an all-inorganic device architecture combined with utilizing tens-of-nanometers-sized CsPbBr3 (TNS-CsPbBr3) emitters in a carrier-confined heterostructure to realize green PeLEDs that exhibit high EQEs and low efficiency roll-off. A typical type-I heterojunction containing TNS-CsPbBr3 crystals and wide-bandgap Cs4PbBr6 within a grain is formed by carefully controlling the precursor ratio. These heterostructured TNS-CsPbBr3 emitters simultaneously enhance carrier confinement and retain low Auger recombination under a large injected carrier density. Benefiting from a simple device architecture consisting of an emissive layer and an oxide electron-transporting layer, the PeLEDs exhibit a sub-bandgap turn-on voltage of 2.0 V and steeply rising luminance. In consequence, we achieved green PeLEDs demonstrating a peak EQE of 17.0% at the brightness of 36,000 cd m-2, and the EQE remained at 15.7% and 12.6% at the brightness of 100,000 and 200,000 cd m-2, respectively. In addition, our results underscore the role of interface degradation during device operation as a factor in device failure.

Highly efficient white organic Light-Emitting diodes utilizing intermolecular interaction based on molecular geometry between host and deep blue Pt(Ⅱ) complex

Previous studies on white organic light-emitting diodes (WOLEDs) using a single Pt dopant relied on square-planar Pt complexes, exhibiting various emission characteristics due to ligand-centered π-π interactions. However, this approach limits the range of the materials selections to those with excimer or aggregation-induced emission (AIE) properties.In this study, a new method for creating WOLEDs with a single Pt dopant is proposed. We observed the emergence of an intermolecular interaction, specifically the formation of an exciplex due to π-π interaction between the n-host (ET) and the Pt complex, leading to a low-energy yellow emission. By varying the mixing ratio of ET and Pt complex, a spectrum of emissions ranging from pure blue to yellow was achievable. Consequently, we constructed 3-stack tandem devices, leveraging color variations based on the ET:Pt ratio. As a result, we successfully achieved a cool white emission with a Color Rendering Index (CRI) of 66.7, International Commission on Illumination (CIE) coordinates of (0.294, 0.380). Additionally, through optimization of the device structure, external quantum efficiency (EQE) was enhanced from 18.3% to 21.9%. This novel and simple device architecture adjusting intermolecular interaction based on molecular geometry between ET and Pt(II) complex provides a solution to materials limitations in WOLEDs.

Tunable Microwave Absorbing Devices Enabled by Reversible Metal Electrodeposition.

Tunable microwave absorbers have gained significant interest due to their capability to actively control microwaves. However, the existing architecture-change-based approach lacks flexibility, and the active-element-based approach is constrained by a narrowband operation or small dynamic modulation range. Here, a novel electrically tunable microwave absorbing device (TMAD) is demonstrated that can achieve dynamic tuning of the average reflection amplitude between -13.0 and -1.2 dB over a broadband range of 8-18 GHz enabled by reversible metal electrodeposition. This reversible tunability is achieved by electrodepositing silver (Ag) layers with controlled morphology on nanoscopic platinum (Pt) films in a device structure similar to a tunable Salisbury screen, employing Ag electrodeposited on Pt films as the modifiable resistive layer. Furthermore, this TMAD possesses a simple device architecture, excellent bistability, and multispectral compatibility. Our approach offers a new strategy for dynamically manipulating microwaves, which has potential utility in intelligent camouflage and communication systems.

OLEDs on Down-Converting Fabric by Using a High Scalable Planarization Process and a Transparent Polymeric Electrode

Textile-based electronics represents a key technology for the development of wearable devices. Light-emitting textiles based on OLED architecture are particularly promising due to their intrinsic flexibility and possibility to be fabricated on large areas using scalable processes. Fabric planarization is one of the most critical issues in their fabrication. Here we report a fast, simple, and industrially scalable planarization method based on the transfer of surface morphological properties from silicon to fabric. A liquid resin is used as a planarization layer, and by exploiting the low roughness of a ‘guide substrate’ it is possible to replicate the smooth and uniform surface from the silicon to the planarization layer. The result is a fabric with a flat and homogeneous polymer layer on its surface, suitable for OLED fabrication. In particular, the effect of resin viscosity on the surface morphology was evaluated to obtain the best planarization layer. The best device shows high luminance and current efficiency values, even after 1000 bending cycles. We also explored the possibility of tuning the color emitted by the device by using a fluorescent fabric as a down-converting layer. Thanks to this approach, it is in principle possible to achieve white emission from a very simple device architecture.

A simple 230 MHz photodetector based on exfoliated WSe2 multilayers.

We demonstrate 230 MHz photodetection and a switching energy of merely 27 fJ using WSe2 multilayers and a very simple device architecture. This improvement over previous, slower WSe2 devices is enabled by systematically reducing the RC constant of devices through decreasing the photoresistance and capacitance. In contrast to MoS2, reducing the WSe2 thickness toward a monolayer only weakly decreases the response time, highlighting that ultrafast photodetection is also possible with atomically thin WSe2. Our work provides new insights into the temporal limits of pure transition metal dichalcogenide photodetectors and suggests that gigahertz photodetection with these materials should be feasible.

Low temperature passivation of silicon surfaces for enhanced performance of Schottky-barrier MOSFET

By using a simple device architecture along with a simple process design and a low thermal-budget of a maximum of 100 °C for passivating metal/semiconductor interfaces, a Schottky barrier MOSFET device with a low subthreshold slope of 70 mV dec−1 could be developed. This device is enabled after passivation of the metal/silicon interface (found at the source/drain regions) with ultra-thin SiO x films, followed by the e-beam evaporation of high- quality aluminum and by using atomic-layer deposition for HfO2 as a gate oxide. All of these fabrication steps were designed in a sequential process so that a gate-last recipe could minimize the defect density at the aluminum/silicon and HfO2/silicon interfaces, thus preserving the Schottky barrier height and ultimately, the outstanding performance of the transistor. This device is fully integrated into silicon after standard CMOS-compatible processing, so that it could be easily adopted into front-end-of-line or even in back-end-of-line stages of an integrated circuit, where low thermal budget is required and where its functionality could be increased by developing additional and fast logic.

Alternating Current Electroluminescence for Human-Interactive Sensing Displays.

The development of stimuli-interactive displays based on alternating current (AC)-driven electroluminescence (EL) is of great interest, owing to their simple device architectures suitable for wearable applications requiring resilient mechanical flexibility and stretchability. AC-EL displays can serve as emerging platforms for various human-interactive sensing displays (HISDs) where human information is electrically detected and directly visualized using EL, promoting the development of the interaction of human-machine technologies. This review provides a holistic overview of the latest developments in AC-EL displays with an emphasis on their applications for HISDs. AC-EL displays based on exciton recombination or impact excitations of hot electrons are classified into four representative groups depending upon their device architecture: 1) displays without insulating layers, 2) displays with single insulating layers, 3) displays with double insulating layers, and 4) displays with EL materials embedded in an insulating matrix. State-of-the-art AC HISDs are discussed. Furthermore, emerging stimuli-interactive AC-EL displays are described, followed by a discussion of scientific and engineering challenges and perspectives for future stimuli-interactive AC-EL displays serving as photo-electronic human-machine interfaces.

Wavelength-Controlled Photoconductance Polarity Switching via Harnessing Defects in Doped PdSe2 for Artificial Synaptic Features.

Optoelectronic synapses are currently drawing significant attention as fundamental building blocks of neuromorphic computing to mimic brain functions. In this study, a two-terminal synaptic device based on a doped PdSe2 flake is proposed to imitate the key neural functions in an optical pathway. Due to the wavelength-dependent desorption of oxygen clusters near the intrinsic selenide vacancy defects, the doped PdSe2 photodetector achieves a high negative photoresponsivity of -7.8 × 103 A W-1 at 473nm and a positive photoresponsivity of 181 A W-1 at 1064nm. This wavelength-selective bi-direction photoresponse endows an all-optical pathway to imitate the fundamental functions of artificial synapses on a device level, such as psychological learning and forgetting capability, as well as dynamic logic functions. The underpinning photoresponse is further demonstrated on a flexible platform, providing a viable technology for neuromorphic computing in wearable electronics. Furthermore, the p-type doping results in an effective increase of the channel's electrical conductivity and a significant reduction in power consumption. Such low-power-consuming optical synapses with simple device architecture and low-dimensional features demonstrate tremendous promise for building multifunctional artificial neuromorphic systems in the future.

Regulating energy gap in Ir-based ionic complexes to generate near-infrared emissions: Application in solid-state light-emitting electrochemical cells

Solid-state light-emitting electrochemical cells (LECs) exhibit high potential for commercial electronics owing to their simple solution-processable device architectures, low-voltage operation, and compatibility with inert metal electrodes. However, the low device efficiency of most deep-red and near-infrared (NIR) LECs hinders their application (external quantum efficiency (EQE) < 1.00%). In this study, we demonstrate a simple method to tune the energy gap between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) of iridium-based ionic transition metal complexes (iTMCs) to generate NIR emissions. We investigate a series of cationic iridium complexes with small energy gaps, with 2,2′-bibenzo[d]thiazole fixed as N^N ligand moiety mainly controlling the LUMO energy level, changing a series of C^N ligands. All complexes exhibited deep red/NIR phosphorescence, and these combined devices provided emission peaks at 690–730 nm and were applied as components in LECs, exhibiting a maximum EQE of 1.78% in electroluminescence devices. Using a host–guest emission system with the iridium complex YIr as the host and complex TBBI as the guest, the highest EQE of LECs could be further enhanced to>2.34%, which is the highest value reported for NIR LECs.

Exfoliated Se nanoparticles decorated on MoS2/paper-based heterojunction as a flexible, self-powered and highly responsive photodetector

Self-powered heterostructure based photodetectors are of great research interest owing to their zero-power consumption, enhanced light-matter interaction, and the ability to respond in harsh environmental conditions. Selenium (Se) nanoparticles have been recently explored in photodetectors due to their high absorption coefficient and superior light-sensing ability. However, most reported Selenium based photoconductors utilize sophisticated device fabrication methodology, requiring regulated environmental conditions, elevated temperature and face flexibility issues. This work demonstrates a discrete(localized) heterojunction of exfoliated Selenium decorated on hydrothermally grown MoS2/paper-based high-performance, flexible, and self-powered photodetector. X-ray Diffraction and Raman Spectroscopy studies reveal the presence of hexagonal Se and the SEM image shows the uniformly grown MoS2 on cellulose paper. It also confirms the presence of Se clustered nanoparticles. The hybrid heterostructure device displays broadband response in the Vis-NIR region. Upon light illumination, a built-in field is generated due to the efficient separation of the charge carriers, making the fabricated device to operate at zero bias. The as-fabricated device exhibits superior responsivity of 0.14 A/W and 0.49 A/W and detectivity of 4.55 × 1011 Jones (intensity- 35.8 mW/cm2) and 5.01 × 1010 Jones (intensity- 30.08 mW/cm2) upon Vis and NIR irradiation, respectively, at no bias. This superior performance is asserted to the peak absorption of Se nanoparticles in the NIR region. The device also showed superior resistance to bending stress and retained its original characteristics even after multiple bending cycles (∼1050). Hence, with this facile device fabrication and simple device architecture strategy, this work paves the way for developing high-performance tensile photodetectors.

Plasmon-enhanced photodetectors fabricated using digital inkjet-printing on chemically nanopatterned silicon wafers

In this study, we have fabricated and characterized three different configurations of photodetectors with digital inkjet printing techniques on different types of silicon substrates, such as pristine n-type silicon and chemically nanostructured n-type silicon, with and without Ag nanoparticle-induced surface-plasmon enhancement. Among these three comparison batches, digitally printed devices on chemically nanostructured n-type silicon with Ag nanoparticle-induced enhancement yield the highest photocurrent enhancement factor of 920×, the lowest rise and decay times of τr = 176 ms and τd = 98 ms, respectively, and the highest responsivity of 24.8 mA W−1 at wavelengths ranging from 380 to 700 nm. Most importantly, we demonstrate that these devices are highly stable after fabrication, losing less than 3% of their efficiency over 60 days under ambient conditions. We firmly believe that this simple device architecture and effective digital fabrication process are most promising for the realization of efficient, stable, and low-cost photodetectors fabricated at large scales.

Suppression of Mid‐Gap Trap State in CsPbBr3 Nanocrystals with Br‐Passivation for Self‐Powered Photodetector

All‐inorganic halide perovskite nanocrystals (NCs) have attracted great attention, prized for their excellent photophysical properties. However, the insulating nature of alkylamine ligands impede the electrical performance of optoelectronic devices. The control content of passivating ligands and suppression of mid‐gap trap state from perovskite NCs is an essential step to boost the device performance. Therefore, in this report a facile one step ligand‐exchange procedure is employed by rinsing the perovskite film into excess of bromide content to passivate surface trap state along with the suppression of native alkylamine ligands. Remarkably, owing to the vacancies filling potential of cesium bromide, hysteresis behavior in the treated perovskite film was significantly suppressed. More importantly, the absorption and photoluminescence intensities as well as photoluminescence quantum yield of bromide passivated films were improved. The heterojunction photodetector based on the configuration of indium tin oxide (ITO)/ZnO/CsPbBr3‐CsBr/Au revealed a higher responsivity of 6.38 A W−1, fast response time of 270/277 ms and a higher value of specific detectivity 2.6 × 1013 Jones. This work provide a facile and effective approach to effectively passivate the surface trap states from perovskite NCs with control value of native alkylamine ligands. The simple device architecture further provides a promising approach to fabricate high performance self‐powered photodetectors.

White Light-Emitting Electrochemical Cells Employing Phosphor-Sensitized Thermally Activated Delayed Fluorescence to Approach All-Phosphorescent Device Efficiencies.

Solid-state light-emitting electrochemical cells (LECs) show promising advantages of simple device architecture, low operation voltage, and insensitivity to the electrode work functions such that they have high potential in low-cost display and lighting applications. In this work, novel white LECs based on phosphor-sensitized thermally activated delayed fluorescence (TADF) are proposed. The emissive layer of these white LECs is composed of a blue-green phosphorescent host doped with a deep-red TADF guest. Efficient singlet-to-triplet intersystem crossing (ISC) on the phosphorescent host and the subsequent Förster energy transfer from the host triplet excitons to guest singlet excitons can make use of both singlet and triplet excitons on the host. With the good spectral overlap between the host emission and the guest absorption, 0.075 wt.% guest doping is sufficient to cause substantial energy transfer efficiency (ca. 40 %). In addition, such a low guest concentration also reduces the self-quenching effect and a high photoluminescence quantum yield of up to 84 % ensures high device efficiency. The phosphor-sensitized TADF white LECs indeed show a high external quantum efficiency of 9.6 %, which is comparable with all-phosphorescent white LECs. By employing diffusive substrates to extract the light trapped in the substrate, the device efficiency can be further improved by ca. 50 %. In the meantime, the intrinsic EL spectrum and device lifetime of the white LECs recover since the microcavity effect is destroyed. This work successfully demonstrates that the phosphor-sensitized TADF white LECs are potential candidates for efficient white light-emitting devices.

Metal Oxide Films as Charge Transport Layers for Solution-Processed Polymer Light-Emitting Diodes

Here, we discuss the use of metal oxide films as charge transport layers in polymer light-emitting diodes containing poly(9,9-dioctyl-9H-fluorene-2,7-diyl) (PFO) as emissive layer. A simple device architecture consisting of glass-ITO | poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS) | poly(9-vinylcarbazole) (PVK) | PFO | Ca | Al was used as starting point. This device assembly allows the investigation of basic properties of polymeric emitting layers, but does not provide stable devices with high performances. Thus, a more complex, multilayered diode structure is needed. We pursuit that goal with focus on the use of low-cost, easily processed materials. At one side, solution-processed non-stoichiometric MoOx films were used to replace the PEDOT:PSS as hole transport layer. At the other interface, solution-processed ZnO films containing either the bare oxide or a ZnO/carbon dots composite were introduced as electron transport layer. By tunning the characteristics of the metal oxide films, the performance of the blue-emitting PFO-based polymer light-emitting diodes (PLEDs) was massively enhanced.