The invention provides a light emitting device, comprising: a first electrode; a second electrode; a light emitting layer disposed between the first electrode and the second electrode, wherein the light emitting layer comprises an emitting material having a first triplet energy level (T1); and an exciton quenching layer disposed between the light emitting layer and the second electrode, wherein the exciton quenching layer comprises a non-emitting quenching material having a second triplet energy level (T1); wherein the exciton quenching layer is disposed adjacent to the light emitting layer; wherein the emitting material emits by phosphorescence or delayed fluorescence; and wherein the first triplet energy level (T1) is higher than the second triplet energy level (T1). Methods of making the same are also provided.