Pulsed laser deposition of small molecules for organic electroluminescence

A XeCl excimer laser at 308 nm is used for the pulsed laser deposition (PLD) of a range of novel electroluminescent molecules. An optimum fluence dependent on the absorption length is found as a compromise between deposition rate and photodecomposition. There is minimal degradation of the aromatic luminescent core of the molecule when the fluence is optimised. Electroluminescent devices are prepared and show similar properties to those incorporating spin-cast films. Photodecomposition is observed for films deposited using higher fluences. The decomposition mechanism is ablative and some photoproducts are oxidised at high fluences. Thin films of reactive mesogens, containing end-groups which can undergo free radical polymerisation, are also prepared by PLD. These are not polymerised on the substrate by the deposition process. Subsequent irradiation with ultraviolet light results in an insoluble cross-linked network.