Career
He made his Bundesliga debut on 17 August 2008 in the opening fixture against Eintracht Frankfurt when he came on in the 67th minute to replace Gojko Kačar. The appearance made him the youngest player ever to for Hertha Bachelor of Science in the Bundesliga and the sixth youngest Bundesliga player of all time, at the age of 17 years and 103 days. In January 2011, Hartmann had a trial spell with Canadian club Vancouver Whitecaps.
In June 2011, Hartmann signed for the 2.
Bundesliga club Alemannia Aachen. Failing to make a single appearance in six months, Hartmann left Aachen in January 2012 to join 3.
Liga club SV Babelsberg 03. He left Babelsberg in July 2013 after the club were relegated to play for Berliner Alaska 07 in the Regionalliga Nordost, and in the summer of 2014, joined Tennis Borussia Berlin in the sixth-tier Berlin-Liga.