A light emitting device and a displaying device. The light emitting device includes a luminescent layer, wherein the luminescent layer includes a thermally activated delayed-fluorescence material; the thermally activated delayed-fluorescence material includes a donor group, a receptor group and a linking group; the donor group and the receptor group bond to the linking group; and a torsion angle between a plane where the donor group is located and a plane where the linking group is located is θ1, and a torsion angle between a plane where the receptor group is located and the plane where the linking group is located is θ2; wherein θ1 and θ2 enable an energy-level difference between a singlet-state energy level of the thermally activated delayed-fluorescence material and a triplet-state energy level of the thermally activated delayed-fluorescence material to be less than a constant quantity T, wherein 0 eV