The latest advances in the use of solution processable organic semiconductor blends for organic field effect transistor (OFET) applications are reviewed. We summarise multi-component, thin film microstructure formation from solution with particular focus on phase separation and crystallisation of components. These approaches can then be applied to semiconducting materials and their use in organic devices. Several key applications are studied, namely ambipolar systems with n- and p-type components, high charge carrier mobility and uniform films for high performance OFETs, and the potential for self-assembly during OFET fabrication. Blending materials can in all cases be used to combine the advantageous properties of the individual components.