High-efficiency blue multilayer polymer light-emitting diode based on poly(9,9-dioctylfluorene)

Abstract

A highly efficient blue polymer light-emitting diode based exclusively on commercial poly͑9,9-dioctylfluorene͒ and poly͓͑9,9-dioctylfluorenyl-2,7-diyl͒-co-͑4,4Ј-͑N-͑4-s-butylphenyl͒͒ diphenylamine͔͒ is demonstrated. High electroluminescent efficiency is achieved by enhancing electron currents and making devices in multilayered structures. CsF/ Al is used as the efficient electron injection cathode, and the fabrication process is in the glove box to enhance electron mobility by reducing oxygen adsorption. The multilayer structure is prepared by the liquid buffer layer technique. The maximum efficiency is 2.5 cd/ A at deep blue with the corresponding external quantum efficiency of 2%.

Bright Blue Solution Processed Triple‐Layer Polymer Light‐Emitting Diodes Realized by Thermal Layer Stabilization and Orthogonal Solvents

“…Compared to already reported results, the utilization of TFB–stabilized by thermal treatment–as an HTL in PLEDs resulted in similar relative enhancement to the device performance as presented in previous work 15. In addition, a comparison of the results presented in this current work to those achieved by Sax et al,13 using a similar polar soluble fluorene based polymer, suggests that PEGPF is also suitable as ETL for other commonly used polymers like polyfluorene or polyindenofluorene.…”

“…This allows good charge carrier confinement within the EML, resulting in an enhancement of the maximum luminance and electroluminescence efficiency for multilayer PLEDs in comparison to single layer devices. Furthermore, the magnitude of the improvement is in the same range as for previously reported works on PLEDs with an assembly based on polar soluble polyfluorene,13 thermally crosslinked30–32 or thermally stabilized polymer interlayers 14, 15…”

“…To implement multilayer device structures by subsequent solution processing of different layers, care has to be taken by the selection of solvents and materials to ensure that upon deposition of the sequent material the preceding layer does not redissolve. Different approaches addressing this issue were already presented and are based mostly on crosslinking reactions,9–11 use of orthogonal solvents,12, 13 a layer‐stabilizing “hard‐bake” process14 or on liquid buffer layers in between when applying the subsequent polymer layer 15…”

Synthesis and characterization of new polyfluorene derivatives: using phenanthro[9,10-d]imidazole group as a building block for deep blue light-emitting polymer

“…The high-energy gap essential for deep blue light emitting polymer often results in low electron affinities, which hampers the electron injection and the balance of the charge carriers [14,15]. To solve the problem, multilayered structure which constitutes an electron transport layer, an emitting layer and a hole transport layer are widely applied to improve the performance of the devices [16][17][18][19][20][21]. But the sequential deposition of these layers provides additional complexity and the cost of such devices will be increased.…”

Influence of the polymer concentration on the electroluminescence of ZnO nanorod/polymer hybrid light emitting diodes

“…PFO is well known for its blue emission together with interesting electrical and electro-optical properties, making it suitable for polymer light emitting diode applications. 10,11 PFO also has a simple chemical structure but is rich in morphological features, depending on the processing conditions used, which can affect the device performance and the emission color. 12 It should be noted that polymer LEDs suffer from several disadvantages, including the lack of the stable n-type polymer necessary for device efficiency and long-term operational stability.…”