Heeger 9510387 The discovery of polymer light-emitting diodes (LEDs) with relatively high quantum efficiency has opened an important new direction for research and has expanded the possible applications for conducting polymers in the area of active light sources. With a goal of achieving high quantum efficiency electroluminescence in polymer LEDs, this research program addresses the basic physics of pi-electrons in conjugated polymers. The experimental methods focus on the use of ultrafast time-resolved spectroscopy (resolution less than a pico- second), including sub pico-second time-resolved photoinduced absorption, sub pico-second time-resolved luminescence and pump-probe experiments to characterize the possible role of stimulated emission. The research will focus on dilute blends of semiconducting luminescent polymers. %%% The discovery of polymer light-emitting diodes (LEDs) with relatively high quantum efficiency has opened an important new direction for research and has expanded the possible applications for conducting polymers in the area of active light sources. The potential importance of this area had been recently highlighted in President Clinton's report on Science in the National Interest ("Polymers that Glow"). With a goal of achieving high quantum efficiency electroluminescence in polymer LEDs, this research program addresses the basic physics of pi-electrons in conjugated polymers through studies of photoinduced luminescence and photo-induced charge/energy transfer. The experimental methods focus on the use of ultrafast time-resolved spectroscopy resolution (less than a pico-second). ***