The characteristics of photoinduced electron-transfer reactions, thermoluminescence, and organic light-emitting diodes (OLEDs) using arylated methylenecyclopropanes are described from a mechanistic perspective. A mechanistically unique OLED, called an "organic radical light-emitting diode," or ORLED, was designed that makes use of an electronically excited triplet trimethylenemethane biradical. The ORLED approach has the potential of overcoming major problems associated with typical OLED systems, such as difficulties in obtaining long wavelength emissions, low quantum efficiency, and low device durability.