| Summary: | 碩士 === 國立雲林科技大學 === 電子工程系 === 107 === In this study, the performance improvement of flexible blue fluorescent organic light-emitting diodes (OLEDs) has been investigated first with the material matching of hole transport layer (HTL) and electron transport layer (ETL), and the optimization of the HTL thickness. Different materials have different energy levels and carrier mobilities. Therefore, matching of HTL and ETL materials and the optimization of the HTL thickness can optimize the carrier balance of the OLEDs. In this study, the DTT device with PET/ITO/TCTA/MADN/TPBi/LiF/Al structure having TCTA thickness of 60 nm has shown maximum luminance, current density (CD), current efficiency (CE), external quantum efficiency (EQE), power efficiency (PE), and peak wavelength of 1388 cd/m2, 105.36 mA/cm2, 2.31 cd/A, 2.66%, 1.67 lm/W, and 442 nm, respectively. Secondly, the optimization of the emitting layer (EML) has been carried out by changing the deposition rate of EML and the doping concentration to lower the quenching problem. The optimal deposition rate of MADN is 0.5 Å/s with maximum luminance, CD, CE, EQE, PE, and peak wavelength of 1446 cd/m2, 75.58 mA/cm2, 2.48 cd/A, 2.71%, 1.97 lm/W, and 442 nm, respectively. The optimal doping concentration of DSA-Ph is 1% with maximum luminance, CD, CE, EQE, PE, and peak wavelength of 4058 cd/m2, 74.65 mA/m2, 6.48 cd/A, 3.87%, 3.50 lm/W, and 472 nm, respectively. The efficiency and luminance of the blue OLEDs have been increased by 2 times with DSA-Ph doping. Thirdly, the improvement of the OLEDs has been carried out by adding carrier confinement layers (CFLs) including single CFL, double CFLs, hybrid CFLs. Two types of CFL were used in this study, namely the electron confinement layer (ECL) and the hole confinement layer (HCL). For the single CFL and double CFL devices, the device with double ECL (D2ECL) has the highest luminance, CD, CE, EQE, and PE of 11252 cd/m2, 91.22 mA/cm2, 13.12 cd/A, 6.35%, and 6.37 lm/W, respectively. Furthermore, the device with hybrid type CFL (DTC+TP) has even better performance than that of the device with D2ECL. The maximum luminance, CD, CE, EQE, PE of the device with hybrid type CFL are 11050 cd/m2, 85.10 mA/cm2, 14.81 cd/A, 7.27%, and 6.71 lm/W, respectively. Finally, the thicknesses of the CFL were varied for the devices with D2ECL and DTC+TP. The maximum CE, EQE, and PE of the device with D2ECL of 30 Å at 7V are 12.93 cd/A, 6.35%, and 5.80 lm/W, respectively. The maximum CE, EQE, and PE of the device with DTC+TP of 15 Å at 7V are 13.77 cd/A, 6.62%, and 6.18 lm/W, respectively. Consequently, the maximum efficiency of the flexible blue fluorescent OLED has been obtained with the hybrid type CFL (DTC+TP) in this study.
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