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Tham khảo tài liệu 'organic light emitting diode material process and devices part 8', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 166 Organic Light Emitting Diode - Material Process and Devices 100 i 75 50 fi I 25 0 0 0 5 10 15 20 25 30 with iPiCS 13 nm Alq3 50 nm Alq3 75 nm without iPrCS Alq3 50 nm o Alq3 75 nm Voltage V a g 750 S K 500 I 250 1 0 wilh iPrCS 13 nm Alq3 50 nm Alq3 75 nm without iPiCS Alq3 50 nm o Alq3 75 nm 5 10 15 20 25 Voltage V Current Density mA cm2 Fig. 4. a Current voltage b luminescence voltage and c efficiency characteristics of ITO TPD 30nm Alq3 50 75nm Al with and without iPrCS It could be supposed that notwithstanding the iPrCS is an insulator it seems to enhance the hole injection thus improving a hole-electron balance in OLED and makes the tunneling injection in OLED. 2.2 Polycarbonate PC The PC is a rigid transparent and amorphous material with high Tg 140-155 oC. It possesses excellent dielectric and optical characteristics. The possibility of usage of PC as buffer layer in OLED with ITO PC TPD Alq3 Al structure was investigated. The PC layers with thicknesses of 9 12 and 17 nm were deposited via spin-coating from 0.1 0.2 and 0.3 dichlorethane solutions. The basic characteristics of OLED structure with different thickness of PC buffer layer are presented in Fig.5. It was found that inserting of 9 nm buffer layer in OLED devices decreased the turn on voltage from 12.5 to 8 V and increased the current density from 10 to 24 mA cm2 and the luminescence from 220 to 650 cd m2 at 17.5 V compared to the reference structure. Further increasing of the thickness of PC buffer layer decreases the current density and the luminescence and shift the turn on voltage toward higher values Fig.5b as was established with iPrCS. Organic Light Emitting Diodes Based on Novel Zn and Al Complexes 167 S 60 50 40 30 20 10 0 0 5 10 15 20 25 30 Voltage V 750 g 500 2 250 0 PC 9 TPD 30 Alq3 50 0 5 10 15 20 25 30 Voltage V PC 1O tpd 30 Al l.i 50 0 0 25 50 Current Density mA cm s Õ a Ũ Fig. 5. Current voltage 5a luminescence voltage 5b and efficiency 5c for inset in legends structures. The best
