| Organic light-emitting device is regarded as the third promising display device,which can be used in panel display and lighting area.It has numerous characteristics,such as all-solid-state,active emitting,high-light,high contrast,ultrathin,low-cost,quick response,wide angle,wide operating temperature range,low operating voltage,flexible and large area.With the problem of the development of Organic Light-emitting Devices?OLED?,the transparent OLED is also restricted by its efficiency and stability.In addition there is also the most difficult problem of choosing transparent cathode.Thus,In order to improve the transmittance and luminous efficiency of transparent OLED,we did the following work including four aspects:?1?Transparent organic light-emitting device?TOLED?based on a stacked alloy cathode of a LiF/Al:Ag is investigated.In the experiment,it is found that LiF?1nm?/Al:Ag?1:3??75nm?has good electron injection efficiency.Compared to an Al-only cathode,the turn-on voltage is lowered.At the voltage of 10V,the luminance,for bottom emission from ITO anode side and top emission from metal cathode side,is 2459 cd/m2 and 1729 cd/m2,respectively.Thanks to enhancing electron injection by using Al-Ag cathode,can we obtain a better energy level matching between the cathode and the organic layer,thus the transparent device have lower turn-on voltage and higher luminance.The entire transmittance of the device achieves about 40%at a 550 nm wavelength.?2?The cathode mesh mask combined with Al:Ag alloy to prepare the cathode of transparent OLED is adopted,which would enhanced the luminance,efficiency and transmittance of the device.With the same driving voltage,the device has the highest brightness,when the cathode thickness is 85 nm.At the voltage of 13V and 14V,the luminance,for bottom emission and top emission is9501 cd/m2 and 1840 cd/m2 respectively.The entire transmittance of the device has achieved about 78%at a 480 nm wavelength.?3?The SiO2 crystals are added at a certain ratio while the Al:Ag alloy cathode is vapor-deposited.Then the optimum doping ratio and cathode thickness of the device are determined.With the addition of SiO2 crystals,the device's transmittance improves significantly,reaching a maximum of 75.28%,nearly 10%increase compared to the device without SiO2 crystals.When the device cathode thickness is 100nm,the maximum brightness can reach 11090cd/m2,and the efficiency can reach 15.56 cd/A.The transmission rate is greatly increased on the basis of ensuring the brightness and efficiency are not greatly affected.?4?A cationic film-forming agent and a chloride desiccant are combined to form a liquid coating desiccant which has well film-forming property and moisture absorption performance.After the device is prepared,the film desiccant is coated on a pre-prepared glass cover plate by using a conventional packaging method,using a UV curing epoxy resin to complete the encapsulation.Comparing with original desiccant,the process is simple,and can be used for many times,preserved in the air,and the cost of this desiccant is cheaper than others.After 240 hours,the brightness of devices with desiccant film are 103.5%,83.3%and 119.8%of the average,the efficiency of devices are 130.7%,65.6%and 126.0%of the average,respectively.Compared with traditional desiccants,it seems that the encapsulation with the desiccant film is a simple and efficient way to improve the performance of OLED and delay its degradation. |
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