Highly efficient OLED was obtained with 1-methyl-1,2,3,4,5-pentaphenylsilole (MPS) as emission material. The measured 8% of external quantum efficiency is higher than the generally admitted theoretical limit. Sharp dependence on Alq₃ thickness of device efficiency was observed. The concept of electron injector was developed, which is consisting of ultrathin Alq₃, LiF and Al. The concept was verified effective for other silole derivatives studied here. Device with hexaphenylsilole (HPS) emits very bright greenish-blue light, up to 55,880cd/m² at 16V. Emission starts at 2.6V, and reaches 100-cd/m² and 10,790-cd/m² at 5V and 10V respectively. The maximum external quantum efficiency is 7%. Bright and efficient blue OLED were obtained with PPOS as emission layer, the external quantum efficie...[ Read more ]

Highly efficient OLED was obtained with 1-methyl-1,2,3,4,5-pentaphenylsilole (MPS) as emission material. The measured 8% of external quantum efficiency is higher than the generally admitted theoretical limit. Sharp dependence on Alq₃ thickness of device efficiency was observed. The concept of electron injector was developed, which is consisting of ultrathin Alq₃, LiF and Al. The concept was verified effective for other silole derivatives studied here. Device with hexaphenylsilole (HPS) emits very bright greenish-blue light, up to 55,880cd/m² at 16V. Emission starts at 2.6V, and reaches 100-cd/m² and 10,790-cd/m² at 5V and 10V respectively. The maximum external quantum efficiency is 7%. Bright and efficient blue OLED were obtained with PPOS as emission layer, the external quantum efficiency is 4%; Pure blue light emitted from OLED with DMS, the emission spectrum peaks at 472nm.

Based on the dependence of device efficiency on hole injection layer (HTL) thickness, a carrier transport balance model was developed, with which the sharp decrease in EL efficiency with thinner HTL thickness can be well understood. The dependence of EL efficiency on the thin layer of Alq₃ thickness was also explained with the same model. The hypothesis of excessive holes existing within ETL was also proved with experimental results.

Better crystallization of IT0 enhanced the hole injection and increased the device efficiency. With ZnO as a buffer layer, the IT0 showed strong (222) orientation, and greatly improved the OLED device efficiency, even increased by 30% than that on commercial ITO.

Aluminum doped zinc oxide (AZO) thin films were successfully co-sputtered from two separate targets, aluminum and zinc oxide. The acquired lowest resistivity was 1.3x10^-3Ω⋅cm. The OLED device with AZO as anode showed comparable current efficiency and power efficiency (3.7cd/A and 1.21m/W for undoped Alq₃ OLED) with that on ITO.

High DC power of up to 120W was used for sputtering transparent top IT0 as the cathode for OLED devices. A high IT0 deposition rate, 0.1nm/s, has been achieved, much higher than the reported IT0 deposition rate using RF power supply.