Neutron Reflectivity Study for Solution-processed Organic/Organic Interfacial Structures in Organic Light-emitting Devices

Abstract

  Solution- and thermal annealing-processed organic/organic interfacial structures in organic light-emitting devices (OLEDs) were investigated by neutron reflectivity measurement. Two types of solution-processed interfaces, polymer hole-transporting layer (HTL)/small molecules light-emitting layer (EML) and small molecules EML and small molecule electron-transporting layer (ETL) interfaces, were investigated. In the both processes, asymmetric diffusion was observed in the polymer HTL/small molecules EML interface, while interdiffusion was observed in the small molecules EML/small molecule ETL interface. This difference was attributed to the difference of the diffusivity between the small molecules and the polymer. Solution-processed OLEDs were fabricated to investigate correlations between the interfacial structures and their characteristics. Interlayer mixing by the solution-processing brought significant impacts on the device characteristics.