| Organic light-emitting device (OLED) have attracted much attention due to theiradvantages in light weight, low cost, abundant materials, low power consumption, andparticularly, sufficiently ductile of the organic material to undergo significant stresswithout cracking. At present, OLED has been used into a mobile phone and a fewother electronic products. Howerer, it is far away from large scale appilicaton. Theperformances, such as efficiency and lifetime, need to be improved. It is nowappreciated that the electrode/organic functional materials interfaces play animportant role in determining the performance of organic optoelectronic devices. Inthis thesis, much research has been done based on regulation of interface betweenelectrode and organic materials. We have realized the improvement of efficiency,stablility and viewing angle by regulating morphology of interface throughultrasmooth electrode and structured electrode and regulating energy band throughp-doping. The research results include the following aspects:(1) An ultrasmooth Ag film with sub-nanometer surface roughness on flexiblesubstrate has been fabricated by template stripping process and its effect on organicmaterials deposition and carrier injection and transport in OLEDs has beeninvestigated. We demonstrate highly flexible and efficient OLED which based on theultrasmooth electrode. Compared with conventional devices on Si substrate, theefficiency of devices fabricated with ultrasmooth electrode have60%enhancement. These improvements are obviously originated from carrier injection and transportenhancement as a result of lowered surface roughness of Ag electrode. Moreover, wehave demonstrated a structured polymer encapsulation film on top of TOLED whichcan realize the enhancement of light extraction, the prolongation of lifetime bypreventing moisture and oxygen diffusion into the devices. In addition, theencapsulated devices also have the ability of self-cleaning due to the decrease ofpollution by water droplets and dust arising from high contact angle of structuredsurface.(2) An efficient ITO-free flexible OLED with ultrasmooth PEDOT: PSS anodehas been demonstrated. The ultrasmooth polymer electrode have been fabricated andapplied to flexible OLED. Compared to spin-coated PEDOT: PSS film on glasssubstrate, the PEDOT: PSS film on polymer substrate fabricated by employingtemplate stripping process has shown superiority on both conductivity and surfacemorphology. The OLED on polymer substrate has also exhibited higher efficiency. Itsmaximum current efficiency is6.21cd/A, while it is4.71cd/A for that with theas-deposited PEDOT: PSS anode on glass substrate, which corresponds to38%enhancement. To further enhance the conduction of PEDOT: PSS film, H2SO4-treatedhas been used. The effect of residual H2SO4on the surface of PEDOT: PSS in H2SO4treatment has been eliminated by template stripping process.(3) Graphene oxide (GO) has been used as p-dopant into PEDOT: PSS anode toimprove interface between electrode and organic layer. The GO doped into PEDOT:PSS was beneficial to the performance of OLED. The hole-injection ability and electron blocking effect were both improved and the exciton quenching was alsosuppressed. The PEDOT: PSS/GO (15/1) was optimal doping concentration. In caseof this condition, the maximum luminance and efficiency was23871cd/m2and5.71cd/A while they were14415cd/m2and3.67cd/A with undoped PEDOT: PSS anode.(4) WTOLED with angle-independent broadband emission has beendemonstrated by integrating a periodic microstruture into the device structure toconstruct a cavity with gradually changed cavity length. From building a periodicallycorrugated anode and a relatively planar cathode, the shift of the peak emissionwavelength with the viewing angle is successfully suppressed, and moreover, adesired broad emissive spectrum and stable CIE coordinates are both obtained. Thevariation of the CIE coordinates is within±0.01when the viewing angle changedfrom0°to60°. |
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