According to German media reports, the 16-year-old will also receive a signing bonus that is approximately the same as the transfer fee.
The Bundesliga club is activating a buyout clause of just under €10 million (just over 109 million kronor) in Eichhorn's contract with Hertha Berlin.
Bundesliga rival Leipzig was also interested in Eichhorn, who played 17 league games and scored 2 goals last season for Hertha Berlin.
