The on-chip adaptive cell can adjust charging current automatically based on the output capability of input power supply, so SDBK03TA is ideally suited for the solar-powered systems, or the applications that need to charge lithium-ion battery or lithium polymer battery with an input power supply whose output capability is limited.
If your solar panel is 5V, then you can use it directly. Of course, the module can also be powered by a 5V DC power supply.
If your solar panel is larger than 5V(e.g. 6V 9V 12V 18V 24V 36V 48V), you can convert it to 5V with DC-DC buck module(e.g. DD2712SA_5V/DD8024TA_5V).