TFT structure, preparation method thereof, display panel and display device

The invention relates to a TFT structure, a preparation method thereof, a display panel and a display device. The TFT structure comprises a grid electrode, a grid insulating layer, an oxide active layer, a source electrode and a drain electrode, the oxide active layer comprises a first oxide layer, a second oxide layer and a third oxide layer which are stacked, the first oxide layer is adjacent to the grid insulating layer, and the third oxide layer is far away from the grid insulating layer; the second oxide layer is located between the first oxide layer and the third oxide layer; and the mobility of the first oxide layer and the third oxide layer is lower than the mobility of the second oxide layer. According to the TFT structure, light can be prevented from irradiating the second oxide layer through the first oxide layer, so that failure of the TFT structure is avoided; in addition, the third oxide layer can also protect the second oxide layer, so that the second oxide layer is prevented from being pollute