Double Monochromator

Sub-bandgap electronic states, or defect states, are critical to the performance of materials and optoelectronic devices, yet these defect states often go undetected due to the difficulty in directly measuring them. This equipment development grant will establish high sensitivity photoemission spectroscopies for directly probing these important defect states in materials and devices with applications in energy conversion and storage. A laser-excited light source and double monochromator will be purchased for integration with the current photoemission spectroscopy instrumentation in the Graham laboratory. The proposed system will enhance the capabilities of the laboratory’s current photoemission spectroscopy system to allow investigation of surface and interfacial defect states in materials for photovoltaics, thermoelectrics, electrocatalysis, photocatalysis, and organic electronics. Here, the application of this tunable light source will increase the probing range of the density of states from two orders of magnitude to seven orders of magnitude, thereby enabling sub-bandgap defect states to be detected. The instrumentation developed will provide capabilities that are not currently available in any US-based academic research laboratory, with the only similar systems being based in Germany and Japan. Such capabilities will provide the University of Kentucky with state-of-the-art capabilities that will be leveraged by multiple faculty members to strengthen their respective research programs, while also enabling the development of new and impactful collaborations. Adding these complementary photoemission spectroscopies to the suite of defect state characterization methods currently under development in the Graham laboratory will establish UK as a leader in defect state spectroscopies.