Abstract
Solution-processable light-emitting electrochemical cells (LECs) with simple device architecture have become an attractive candidate for application in next generation lighting and flat-panel displays. Herein, single layer LECs employing two cationic Ir(III) complexes showing highly efficient blue-green and yellow electroluminescence with peak current efficiency of 31.6 cd A−1 and 40.6 cd A−1, respectively, have been reported. By using both complexes in the device, color-tunable LECs with a single spectral peak in the wavelength range from 499 to 570 nm were obtained by varying their rations. In addition, the fabrication of efficient LECs was demonstrated based on low cost doctor-blade coating technique, which was compatible with the roll to roll fabrication process for the large size production. In this work, for the first time, 4 inch LEC devices by doctor-blade coating were fabricated, which exhibit the efficiencies of 23.4 cd A−1 and 25.4 cd A−1 for the blue-green and yellow emission, respectively. The exciting results indicated that highly efficient LECs with controllable color could be realized and find practical application in large size lighting and displays.
Highlights
Solution-processable light-emitting electrochemical cells (LECs) with simple device architecture have become an attractive candidate for application in generation lighting and flat-panel displays
The fabrication of efficient LECs was demonstrated based on low cost doctor-blade coating technique, which was compatible with the roll to roll fabrication process for the large size production
For LECs device based on complex Y, the turn on voltage of device decreased from 3.5 V to 3 V; at the same time, the brightness of the device increased from 61.8 cd/m2 to 361 cd/m2 at 6 V; but current efficiency decreased from 25.8 cd A−1 to 12.6 cd A−1 (6 V) due to carrier mismatch
Summary
Iridium Complexes-based Lightemitting Electrochemical Cells received: 13 January 2016 accepted: 20 May 2016. For the first time, 4 inch LEC devices by doctor-blade coating were fabricated, which exhibit the efficiencies of 23.4 cd A−1 and 25.4 cd A−1 for the blue-green and yellow emission, respectively. By varying ratios of blue-green and yellow emitting cationic Ir(III) complexes, the color-tunable LECs devices with a single spectral peak in electroluminescence (EL) spectra were achieved. We report a technique to fabricate high efficiency large area LECs using a doctor-blade coating. The PEDOT:PSS solutions was spin-coated onto ITO-coated glass substrates at 3000 rpm for 40 s and annealed at 160 °C for 20 min in air, yielding a film thickness of about 50 nm. The thickness of the light-emitting layer films was controlled by complex solution concentration, scraping speed and the spacing between steel blade and the substrates. In addition to the deposition of Al electrodes, all fabrications and tests were carried out at room temperature in atmospheric pressure
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