Question

where do the high energy electrons carried by NADPH come from ?

Answer 1

The high energy electrons carried by NADPH are produced from the light absorption in chlorophyll to the chemical reactions throughout the cell.

Answer 2

These electrons work little busses. When the light-dependent reaction occurs, the  high energy electrons from sunlight are transported to the NADP+ (from the Calvin Cycle) turning it to NADPH ready to be used on the light-independent. ;)