Cover story: Liu S H, Zhang L T, Xie W F. Solution processed organic light-emitting devices: structure, device physics and fabrication process[J]. Opto-Electron Eng, 2022, 49(5): 210407

Organic light-emitting devices (OLEDs) have been widely used as smartphone displays, and thus become one of the mainstream display technologies.Solution-processed OLEDs does not require complex and expensive vacuum equipment to keep high vacuum environment, making it possible to significantly reduce the manufacturing cost of OLEDs.At present, the reported solution-processed OLED mainly adopts a system of solution-processed bilayer, that is, a combination of polymer transport layer and polymer or organic small molecule emitting layer.

Prof. Xie Wenfa and his research team review solution-processed OLED from the perspective of material engineering, summarized four solution-processing technologies for OLEDs: spin coating process, spray coating process, blade coating process and inkjet printing process and discussed their problems involved in preparing multilayer structures.As a result, solution-processed multilayer structures can be achieved by the two fabrication processes without using orthogonal solvent system and crosslinking material strategy.In conclusion, multilayer structures are necessary to achieve high-performance for solution-processed OLEDs. Soft pressure processing can not only retain the low-cost advantages of the existing solution-processing technologies, but also avoid the problems caused by the introduction of solvents. Thus, this process could have a great potential in the preparation of low-cost multi-layer OLEDs.