Constructing Novel Interfacial Structures For Organic Light-Emitting Diodes Application

Organic light-emitting diodes?OLEDs?have great potential in the field of solid-state lighting and large-area flat panel displays,and have been well commercialized in mobile display terminals.At present,there are still some problems to be solved in the research and development of OLEDs,such as unbalanced carrier mobility and unsatisfied device stability.In this thesis,the modification of interfacial layers was carried out to improve carrier transport process in the OLEDs.Meanwhile,an emitting layer with novel interfacial structures was designed to optimize both efficiency and device stability.Some useful methods were provided for the research of high-performance and high-stability OLED devices.The main contents are as follows:?1?In order to prevent the acidic anode interface layer-PEDOT:PSS from corroding the electrode,several kinds of alkaline solvent vapors with NH₄⁺were used to treat PEDOT:PSS film for fabricating OLEDs.Comparing with the standard device,the current efficiency?CE?,power efficiency?PE?and external quantum efficiency?EQE?of the devices whose PEDOT:PSS film was treated by ammonia water vapor increased from 26.26 cd/A,21.98 lm/W and 13.73%to 31.41 cd/A,25.58 lm/W and16.13%.The X-ray photoelectron spectroscopy,infrared spectroscopy,ultraviolet photoelectron spectroscopy and other tests show that NH₃ reacts with PSS,changing the composition and surface work function in the film,which is beneficial for holes injecting and transporting in PEDOT:PSS film.The locally aggregation of PSS can reduce leakage current,and thus the performance of the device is improved to a certain extent.?2?To further improve the hole mobility of the ammonia water vapor treated PEDOT:PSS film,a method of hot imprinting vapor annealing treatment combining soft template imprinting with ammonia water vapor annealing treatment was developed to process the anode interface layer PEDOT:PSS in OLEDs,and a high-performance blue phosphorescence-OLED?Ph-OLED?was prepared.The CE and PE increased from 26.95 cd/A and 22.05 lm/W to 36.62 cd/A and 27.60 lm/W,respectively.By introducing periodic micro-nano channels,the actual contact area between the layers is increased by about 10%,thereby increasing the hole transport channel in the same effective area and improving the carrier transport capacity.?3?The phase separation problem in the host-guest doped emissive layer is often one of the major causes of unstable OLEDs performance.The structure of spatially separated exciplex and the ultra-thin undoped light-emitting layer as the intermediate layer were designed to prepare the non-doped ultra-thin light-emitting layer Ph-OLEDs device and thermally activated delayed fluorescence OLEDs.In Ph-OLEDs,the energy transfer from the spatially separated exciplex to the emitting material was achieved.The CE and PE of the undoped ultra-thin device increased from 18.70 cd/A and 14.35 lm/W to 38.92 cd/A and 35.84 lm/W,respectively.At the same time,the stability of the devices has also been greatly improved.