Organic compound, light-emitting element, light-emitting device, electronic device, and lighting device
摘要
說明書
<Structure Example 1 of Light-Emitting Element>
The material 131 may be a light-emitting organic material, and the light-emitting organic material is preferably a material capable of emitting fluorescence (hereinafter also referred to as a fluorescent material).
In the light-emitting element 150 of one embodiment of the present invention, voltage application between a pair of electrodes (the electrodes 101 and 102) causes electrons and holes to be injected from the cathode and the anode, respectively, into the EL layer 100 and thus current flows. By recombination of the injected electrons and holes, excitons are formed. The ratio of singlet excitons to triplet excitons (hereinafter referred to as exciton generation probability) which are generated by carrier (electrons and holes) recombination is approximately 1:3 according to the statistically obtained probability. Accordingly, in a light-emitting element that uses a fluorescent material, the probability of generation of singlet excitons, which contribute to light emission, is 25% and the probability of generation of triplet excitons, which do not contribute to light emission, is 75%. Therefore, converting the triplet excitons, which do not contribute to light emission, into singlet excitons, which contribute to light emission, is important for increasing the emission efficiency of the light-emitting element.
