- 标题
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Electrical and Environmental Degradation Causes and Effects in Polyfluorene-Based Polymer Light-Emitting Diodes
摘要： We report on the degradation mechanism of polymer light-emitting diodes (PLEDs) kept in the environment with no encapsulation. The device structure is indium tin oxide (ITO)/poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS)/poly?uorene/aluminum (Al) fabricated by a simple solution-processed method. Its physical, optical and electrical properties were measured over time in order to explore factors resulting in device instability. The sustained decrease in current density and electroluminescence, as well as the appearance of dark spots and electrode delamination, reveal that the device performance tends to degrade in the atmosphere gradually. To clarify the effect of the external electric ?eld on the device degradation process, a device with lower threshold voltage was fabricated and its performance was recorded with and without bias voltage. Also, when the Al cathode of a completely ruined blue PLED was re-deposited, the device started to emit green light, con?rming the irreversible chemical structural changes occurred in the active layer. Noticeably, in addition to cathode delamination, we observed that the rate of luminescence degradation in fabricated PLEDs is more than two times faster than that of the current density. The detailed study of the stability issue in PLEDs, presented in this work, can have great potential importance in the fabrication of other organic electronic devices such as organic solar cells and organic photodetectors due to similar instability factors.
关键词： Degradation,dark spot,luminescence,polymer light-emitting diode
更新于2025-09-23 15:19:57
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24.3: <i>Invited Paper:</i> Printed Electrodes for All‐Solution‐Processed Inverted‐Structure OLEDs
摘要： A key enabling technology for all-printed organic light-emitting diodes is printing electrodes that can be used for anodes or cathodes for conventional or inverted device structures. In both device structures, the first bottom electrodes, which are either transparent or opaque depending on the device structure, are typically printed while the last top electrodes have been deposited by using a vacuum-based evaporation process because when the last top electrodes are fabricated by using a solution-based process, under organic layers are easily damaged during the fabrication process. Although so-called transfer printing process has been often reported for organic devices such as organic solar cells, it has been rarely applied for OLEDs. In addition, no fine patterning has been adopted in such printing processes. As part of our efforts towards all-printed OLEDs, inkjet-printed and/or transfer-printed, finely-patterned PEDOT:PSS electrodes have been investigated in our lab and most recent achievement will be reported in detail. In order to implement all-solution-processed OLEDs, we also studied the inverted-structure OLEDs, which showed comparable results to the conventional structure OLEDs with the vacuum-based deposited electrodes.
关键词： inverted structure,Organic light-emitting diode,OLED,PLED,inkjet-printing,transfer-printing,polymer light-emitting diode
更新于2025-09-19 17:13:59
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Hybrid Color-Tunable Polymer Light-Emitting Diodes Using Electrospraying
摘要： This paper proposes a new paradigm in polymer light-emitting diode (PLED) fabrication by using a uniform electrosprayed microparticle film as the active layer. Among the seven electrospraying parameters analyzed, three crucial parameters are statistically identified and optimized to obtain thin electrosprayed microparticle layers. Using optimized electrospraying conditions, single-color red-emitting PLED (MEH-PPV) with a peak current density of 16.1 mA/mm2 under a 13.5 V bias and a peak external quantum efficiency of 3.2% are successfully fabricated. Finally, a combinatorial approach is implemented using both MEH-PPV (red-emitting) and F8BT (green-emitting) polymer microparticles at different mixing ratios to tune the emission spectrum of the devices. As such, it has been demonstrated that hybrid multilayer films using different organic materials with nonorthogonal solvents can be produced using this new approach. The parameter analysis and color-tunable properties pave the way towards white light PLED fabrication.
关键词： polymer light-emitting diode,F8BT,electrospraying,PLED,MEH-PPV,color-tunable
更新于2025-09-12 10:27:22
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Fabrication of highly transparent and luminescent quantum dot/polymer nanocomposite for light emitting diode using amphiphilic polymer-modified quantum dots
摘要： Herein we present the fabrication of a highly transparent and luminescent quantum dot (QD)/polymer nanocomposite for application in optoelectronic devices. First, we encapsulated CdSe@ZnS/ZnS core/shell QDs with an amphiphilic polymer, i.e., poly(styrene-co-maleic anhydride) (PSMA). By encapsulating QDs with PSMA instead of ligand exchange, the photoluminescence intensity of the QDs could be preserved even after surface modification. Next, the PSMA-modified QDs were used as crosslinkers for the aminopropyl-terminated polydimethylsiloxane (PDMS) resin in a ring-opening reaction between the maleic anhydride of the QDs and the diamines of the PDMS, producing polymer networks at a low curing temperature. This method afforded a nanocomposite with uniform dispersion of QDs even at high QD concentrations (~30 wt%) and superior optical properties compared to a nanocomposite prepared from unmodified QDs and commercial resin. Owing to these enhanced properties, the nanocomposite was used to fabricate a light emitting diode (LED) device, and the luminous efficacy was found to be highest at 1 wt%.
关键词： quantum dots,dispersion,surface modification,amphiphilic polymer,light emitting diode
更新于2025-09-12 10:27:22