The disclosure provides a display panel, a compensation of brightness method and a displaying device. The display panel comprises an array substrate, a luminescent layer, a plurality of optical film layers and a photoelectric sensor, wherein the luminescent layer is located on one side of the array substrate, the array substrate is used for driving the luminescent layer to emit light, the optical film layers are located on a side, away from the array substrate, of the luminescent layer, light emitted by the luminescent layer forms optical waveguide on the array substrate and/or the optical film layers, and the photoelectric sensor is used for acquiring the optical waveguide to perform compensation of brightness on the light emitted by the luminescent layer according to data of the optical waveguide.