Light emission from semiconducting polymers: LEDs, lasers, and white light for the future

High performance photonic and electronic devices fabricate from conjugated polymers have been demonstrated, including light emitting diodes, photovoltaic cells, photodiodes, optocouplers, and thin film transistors. In some cases, performance parameters have been improved to levels comparable to or better than their inorganic counterparts.Notably absent from this list of semiconducting polymer devices is the polymer laser diode. As the first important step in exploring the feasibility of such laser diodes, optically pumped stimulated emission, gain, and lasing have recently been observed in over a dozen different semiconducting polymers representing a variety of molecular structures with emission wavelengths spanning the visible spectrum. Because of their strong absorption, high density of chromophores, and Stokes-shifted luminescence, luminescent semiconducting polymers have potential as low- threshold laser media and as active media in InGaN/polymer hybrid light emitting devices. We give details on an ongoing effort on optically pumped lasers using microcavities and distributed feedback (DFB) and suggest two routes toward fabricating laser diodes using semiconducting polymers. Initial results show that the lasing threshold for DFB laser is one order of magnitude lower than that of a microcavity laser using the same polymer under similar optical pumping conditions.