Why did I shoot the sun with my mobile phone, and the whole sun turned black?

The appearance of light spots should be explained by photographic knowledge. According to my experience, when shooting the strong sun, you can only shoot a big spot, and other places become very dark, which should be the reason for underexposure. What you are talking about is probably caused by overexposure, contrast and glare, and some special functions of the digital camera itself can also cause this situation.

PS: This is not a sunspot. Sunspots don't get photographed like this. The photosphere of the sun can be observed through astronomical equipment (like ordinary optical telescopes). Many black spots, called sunspots, can often be seen on the photosphere. Sunspot is a local strong magnetic field formed by the violent movement of photosphere, and it is an important symbol of photosphere activity. And it is unlikely to be in the center (the size, number, position and shape of sunspots on the sun are different every day).