Solar cells generate voltage by photovoltaic reaction. In fact, there is no current in any battery measured with a multimeter. Because it is not a closed loop. Only when a load is placed and a closed loop is formed will current flow. The current range impedance of the multimeter is very wide, and the principle of measuring current is not to measure the current passing through the multimeter itself, so you cannot measure the current with the multimeter.
In other words, your method of measuring current is wrong.