Our research is focused on two areas: (1) developing high-efficiency and low-cost solar cells, and (2) advancing the technology of organic light emitting diode (OLED) for display and lighting applications. We fabricate thin-film devices using a suite of vacuum deposition and solution process tools, including vapor deposition of multi-component amorphous organic thin films and close-space sublimation of II-VI semiconductors at high temperature to form crystalline films. We design device architectures - planar, bulk, and graded heterojunctions of organic donors and acceptors - for mediating charge generation, recombination, and transport in OLEDs and organic solar cells. We develop low-impedance contacts for electron and hole injections into semi-insulating materials. Our interest in solar cell work includes the development of methods for fabricating high-efficiency CdS/CdTe solar cells with ultra-thin CdTe films, aiming at significant reduction in material usage. We are also interested in further improving organic solar cell efficiency through design of novel device architectures and material compositions. Another major research effort is to advance OLED technology. Specifically we focus on developing highly stable and efficient white emitters for lighting applications, including light-scattering layers for enhanced light extraction.