Organic Electronics最新文献

A slit nozzle with a broad viscosity spectrum is highly demanded for slit coating of various materials with different viscosities without a compromise on the film quality. To this end, we have fabricated a multi-cavity slit nozzle with the inlet and vent holes for each cavity. Compared with a slit nozzle with a high-volume single cavity, such a multi-cavity slit nozzle further reduces the dead volume and thus material waste. As a design parameter in computational fluid dynamics (CFD) simulations for the multi-cavity slit nozzles, we have calculated the coefficient of variation in the internal pressure (P_cv) of the cavity and investigated the correlation between the simulated P_cv value and the measured thickness uniformity of low-viscosity (tens of cPs) poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS), medium-viscosity (5000 cPs) polydimethylsiloxane (PDMS), and high-viscosity (18,000 cPs) hard-PDMS films. It is addressed that the P_cv value that can ensure the thickness non-uniformity of less than 5 % is of the order of 1 %, and the internal pressure of the nozzle should not exceed a specific upper limit to protect a coating system against overload. Based on the design guideline provided, we have found that the upper limit of the viscosity spectrum of the triple-cavity slit nozzle with the 800-μm-thick shim is 79,000 cPs when the flow rate is 50 ml/min. Using the multi-cavity slit nozzle, we have fabricated a highly uniform PDMS film exhibiting the tensile strain as high as 180 %, which can be used as a substrate for stretchable displays. Furthermore, we have successfully fabricated flexible OLED stripes on the slit-coated conductive PEDOT:PSS stripes, showing the average luminance of 72.8 cd/m² at 5 V and inter-stripe luminance non-uniformity as low as 8.2 %.

In this work, we synthesized poly(3,4-ethylenedioxythiophene): poly (styrene sulfonate) (PEDOT: PSS) and PEDOT: PSS/Bi₂Te₃ hybrid composite film using a spin coating method. The maximum Seebeck coefficient (22 μVK⁻¹) and power factor (57.18 μWm^-1 K⁻² around 300 K) were achieved at 0.4 wt% Bi₂Te₃. The electrical conductivity (σ) reached a maximum of 1467 Scm⁻¹ at 300 K for 0.6 wt% Bi₂Te₃, which is more than three times higher than that of pure PEDOT: PSS. Two critical components contribute to the improved electrical transport performance, as identified by XRD, Raman spectroscopy, XPS, AFM, and SEM. First, the conductive polymer undergoes a structural transformation from a benzenoid to a quinoid configuration, enhancing conductivity. This transformation is due to the interaction between the π bonds of PEDOT: PSS and the Van der Waals forces between the tellurium (Te) atom layers of Bi₂Te₃. Second, the interfacial barrier between PEDOT: PSS and Bi₂Te₃ creates an energy-filtering effect that increases the Seebeck coefficient.

Doctor-blade coating technology is a roll-to-roll compatible high-throughput thin film fabrication route. In this work, doctor-blading was applied for fabricating organic solar cells (OSCs) using a polyoxometalates material phosphomolybdic acid (PMA) as a hole transport layer (HTL). Compared to PEDOT:PSS, PMA-based devices demonstrate lower trap-assisted recombination, higher hole mobility, prolonged charge carrier lifetime and faster charge collection. With PM6:Y6 as active layer, PMA-based device delivered a high power conversion efficiency (PCE) of 17.79 % with a boosted short-circuit current density (J_SC) value of 28.08 mA/cm², which is one of the best performances for PM6:Y6-based solar cells through doctor-blading process. In addition, the performance improvement was observed in both conventional and inverted structured devices with various donor: acceptor combinations. These results indicate the high universality of PMA for printable processing and its prospect in preparation of the industrial production of OSCs.

The inverted p-i-n PSCs are gradually gaining more attention since they are generally more stable and can employ low-cost transport materials. However, the interfaces between the perovskite and the charge transport layers contribute to major power conversion efficiency (PCE) loss and instability. Here, we use a material of 6-(Trifluoromethyl)pyridine-3-amidinehydrochloride (CF₃-PyFACl) to molecularly engineer the interface between the perovskite and electron transport layer. The interface modification results in suppressed nonradiative recombination, and improved interfacial contact. A PCE of 23.17 % is demonstrated, with open-circuit voltage (V_oc) and fill factor (FF) of 1.169 V and 84.1 %, respectively. The unencapsulated device retains >80 % of the initial performance after 400 h continuous light soaking.

In this study, perovskite solar cells (PSCs) were fabricated using a two-step solution deposition method. A laser beam was applied at the interface between lead iodide (PbI₂) and methylammonium iodide to change the reaction temperature and stimulate the growth of perovskite crystals. A notable enhancement was observed in the power conversion efficiency of PSCs. The laser scanning speed was investigated to control the reaction temperature and further control the crystallization and morphology of the perovskite film. Based on the optimized laser scanning speed, the best and average PCEs obtained were 14.33 % and 13.92 ± 0.52 %, respectively, which were higher than those achieved using the conventional technique (12.18 % and 11.37 ± 0.74 %, respectively) and the conventional heating methods (14.09 % and 13.28 ± 0.56 %, respectively). The optimal reaction temperature at the interface was predicted to be 80 °C under optimized conditions using the COMSOL software. This study will help in scaling this technique for large–area PSCs, optimizing the laser parameters for different perovskite compositions, and investigating the long-term stability of enhanced PSCs, boosting their commercial viability.

Conductivity modulations in resistive random access memory (RRAM) devices are currently being extensively investigated for neuromorphic applications. In this work, a detailed investigation of the conductivity modulation in a bio-material-based resistive-switching write-once-read-many times (WORM) memory device is reported for the first time. Sodium caseinate (NaCas) biopolymer, extracted from the bovine milk, is used as the active layer for the WORM device. Our investigations reveal that conductance modulation can be achieved in Ag/NaCas/ITO device structure that exhibits WORM characteristics. It is also demonstrated that the NaCas-based WORM device is capable of exhibiting synaptic emulations like potentiation-depression, short-term-memory to long-term-memory and paired-pulse-facilitation, similar to that reported for the bipolar resistive switching and threshold switching memory devices. Such conductivity modulation in the WORM device may be attributed to the reversible partial alignment of casein micelles present in the active layer.

The pervasive use of zinc oxide (ZnO) as an electron transport layer in quantum dot (QD) electroluminescent devices is constrained due to its chemical instability with the QD layer and the formation of interface quenching sites. The effect of fluorine passivation of sol-gel processed ZnO in QD light-emitting devices (QLEDs) is investigated in depth. An examination of the interaction between the ZnO surface and fluorine species revealed that the passivation of oxygen vacancies and the formation of stable hydrogen bonds with hydroxyl groups on ZnO surface have a significant influence on the stability and efficiency of the device. Such exceptional functions of fluorine have been found to effectively capture defects at the interface between ZnO and the emissive layer, therefore mitigating the interface quenching sites. The initial fluorination device demonstrated a significant improvement in external quantum efficiency (EQE) from 5.72 % to 20.07 %, and half of the device lifetime (LT50 at an initial luminance of 1500 cd m⁻²) was 286 h. Further passivating the remaining active oxygen on the ZnO surface can extend the stability of the device to 542 h with an EQE of 15.2 %, which is among the longest lifetime reported so far for green InP-QLEDs. Our report offers the possibility of utilizing straightforward and highly effective fluorination by spin-coating technique to attain long-lasting InP-QLED devices with remarkable performance.

Perovskite solar cells (PSCs) are emerging as leading contenders in next-generation photovoltaic technology due to their high theoretical power conversion efficiency (PCE) limits and reduced fabrication costs. Organic framework materials, celebrated for their vast specific surface areas, abundant binding sites, tunable nanostructures, and synergistic effects, are extensively utilized to assist in the fabrication of PSCs. These materials are primarily employed to enhance the photovoltaic performance of PSCs. This review systematically explores the synthesis and functionalization of organic framework materials and their application across various layers of PSCs. Additionally, this review delves into how early-stage MOF synthesis routes and functionalization techniques impact the modification outcomes of later-stage MOF-modified PSCs. Finally, this review offers conclusions and prospects for organic framework materials in PSCs.

The interest in all-inorganic perovskite solar cells (PSCs) featuring a p-i-n structure is on the rise, attributed to their superior heat resistance and adaptability with tandem cell methods. However, their progress has been far from the regular structure owing to the comparatively low open circuit voltage (V_oc). This research employs phenylethylammonium iodide, incorporating various side groups, as passivators to tackle the previously mentioned problems and investigate their effects on passivation. It is found that a reduction of trap-state density in perovskite film was accomplished due to the PEAI effective passivation effect by establishing coordination with the under-coordinated Pb²⁺ ions. Furthermore, there was an enhancement in the alignment of energy levels at the CsPbI₂Br perovskite/PCBM junction, resulting in better charge extraction from the CsPbI₂Br layer to the charge transport layer. As a result, an improved champion efficiency of 14.26 % with a V_oc of 1.11 V, J_sc of 16.21 mA/cm², and FF of 79.28 % was yielded for the PEAI treatment inverted CsPbI₂Br device, compared with the 12.15 % efficiency of the control device. Superior device stability was exhibited for the optimal PEAI-treated devices without encapsulation. This research validates the significance of a side group on a surface passivation molecule to effectively passivate defects and optimize energy levels, especially for boosting V_oc.

Solution-processed organic light-emitting diodes (OLEDs) remain a reliable approach towards large-area and flexible display devices, but also hold higher requirement on luminescent materials. It is still challenge to develop emitting layers with great solution-processable property and excellent luminous behavior, and especially difficult for non-doped emitting materials. In this work, a TADF emitter, namely 2,3,5,6-tetrakis(4-([1,1':3′,1″-terphenyl]-5′-yl)-9H-carbazol-9-yl)benzonitrile (3Ph-4CzBN), was designed and synthesized by introducing the steric-hindrance triphenyl unit to 2,3,5,6-tetrakis(carbazol-9-yl) benzonitrile (4CzBN) which is usually applied to vacuum evaporation. The incorporation of triphenyl groups significantly increased the molecule weight, thereby rendering 3Ph-4CzBN suitable for solution-processed OLEDs. Meanwhile, 3Ph-4CzBN exhibited two-fold of photoluminescence quantum yield values in pure film than 4CzBN, indicating fluorescence quenching was relatively suppressed by steric groups. The solution-processed OLEDs employed 3Ph-4CzBN as non-doped emitting layer, achieved a maximum external quantum efficiency of 12.8 %, as well as current efficiency and power efficiency up to 34.2 cd A⁻¹ and 23.9 lm W⁻¹, respectively.