"I am sad to see Stephan go, but glad that he will be given an opportunity to play regular first-team football at a high level," Addicks boss Les Reed told the club's official website.
"It has been frustrating for Stephan as Scott Carson has been in outstanding form this season and there have been limited opportunities for him to play in the first team.
"It's better for him and his own career development to take an opportunity like this and it also allows the club to move on, with Scott and Thomas Myhre as our first-choice keepers."