Soluble pentacene derivatives are high performing semiconductors for use in organic transistors offering low cost solution processability, and potential for migration to flexible substrates. Performance of such materials is limited by an inability to control crystallization over large areas. We have shown that formulation with either a dielectric or semiconducting polymer can give increased control over large area thin film crystallization.We have shown soluble pentacene derivatives form supramolecular aggregates in solution, influenced by additional polymer. We shall study the interrelation between solution aggregation state, thin film crystallization and electrical performance. Small angle neutron scattering can uniquely give us information relative to cluster morphology in solution and we expect this study to lead towards reliable solution processed thin film devices.