Investigating the influence of the solution-processing method on the morphological properties of organic semiconductor films and their impact on OLED performance and lifetime

摘要

The morphological properties of organic semiconductor films deposited by blade coating and spin coating were investigated. The effect of these solution coating methods in fabricating the hole transport layer (HTL) and emissive layer (EML) of OLEDs was also examined. Transient photoluminescence measurements showed that blade-coated films have longer exciton lifetimes than spin-coated films, indicating that blade coating leads to films with less aggregated and more uniform morphologies. OLEDs with a blade-coated CBP:Ir(ppy)_3 EML exhibited an external quantum efficiency (EQE) at 20mA/cm~2 of 8.6% versus 6.4% in case of device with the same structure but with a spin-coated EML. Additionally, the blade coated CBP:Ir(ppy)_3-based device showed a decrease in electroluminescence emission peak by about 52% from its initial value after 20 min of electrical aging, whereas for the spin-coated device, the decrease was 74%. The higher efficiency and longer lifetime in the blade coated devices is likely a result of a more uniform or less aggregated film morphology. These findings demonstrate that blade coating is a promising solution-based fabrication technique to enable more efficient and longer-lived small molecule, solution-coated OLEDs and organic optoelectronic devices.