Solution-casting of electronic devices involves conversion of the semiconductor ink into a thin film using any of a variety of scalable coating techniques: blade coating, slot-die coating, spray coating, gravure coating, ink-jet printing, etc. As the ink building blocks – atoms, molecules, polymers, metal oxides, perovskites, nanocrystals – come closer and pack, interfacial and structural complexity increases. As such, solution coating/printing currently lacks the quality control achievable with the conventional time-consuming single crystal growth platforms that enable defect-free forms of matter. The challenge is to achieve single crystal-like performances in printed electronics without compromising ease of manufacturing. Establishing quality control for printed electronics is key to achieving this goal.
Exquisite control over the coating process can result in non-equilibrium crystal growth and film structures with extraordinary electronic and optoelectronic properties. Photoemission Spectroscopy (PES) is a highly surface-sensitive characterization technique to probe film interfaces that define charge extraction. Microstructure of the resulting film can be explored using synchrotron-based Grazing Incidence X-ray Scattering (GIXS) techniques. Interfacial and structural diagnostics complement each other by revealing film interfaces and microstructure – the two key aspects that define device performance – and can combinedly deliver the much-needed quality control printed electronics requires for market entry.