nm structure as being advantageous but embodiments of the new techniques identified this as a local maximum and enabled a switch to thick ito gt 50 nm thin hil lt 50 nm structures for improved performance referring to fig2 this shows ciex and ciey parameters from a theoretical model of a blue microcavity oled device with the following structure where thicknesses are shown parenthetically in nanometres the variation shown in fig2 is for a simple dipole emitter model assumes optically flat films and requires precise input of many parameters such as refractive index and dielectric constant that may not be accurately known and or may require a time consuming characterisation study this approach is therefore impractical for accurately predicting the output of microcavity inkjet printed devices further as described below the hil layer thickness can vary by up to u2212 50 across a colour sub pixel in a complex manner another approach which may be employed is to fabricate a series of oled devices in which the layers are deposited by spin coating casting so that the edge effects pinning and the like in display pixels are avoided such an approach enables the thicknesses of the layers to be well defined for example to approximately u2212 2 nm and fig3 shows measured variation of the ciex and ciey parameters for.