US Patent 7940002 Light emitting element and light emitting device

A light emitting element of the invention includes n pieces of light emitting layers (n is a natural number) between first and second electrodes. A first layer and a second layer are provided between the mth light emitting layer (m is a natural number of 1≦m≦n) and the m+1th light emitting layer. The first and second layers are contacted to each other. The first layer contain a substance that transports holes easily and a substance with an electron accepting property. The second layer contains a substance that transports electrons easily and a substance with an electron donating property. Molybdenum oxide is used as the substance with the electron accepting property.