A display panel and manufacturing method thereof, a display device and a method of controlling brightness are disclosed. The display panel includes a first transparent electrode layer, a second transparent electrode layer, a dielectric layer and a plurality of charged particles. The first transparent electrode layer is disposed at a light-exiting side of the display panel; the second transparent electrode layer is disposed at a light-incident side of the display panel; the dielectric layer is disposed between the first transparent electrode layer and the second transparent electrode layer. A plurality of charged particles are disposed in the dielectric layer; the refractive index of the second transparent electrode layer is larger than the refractive index of the dielectric layer.