The new R's boss met the club's players on Sunday and his first game in charge will be a trip to fellow strugglers Sunderland on Tuesday.
"I met the lads [on Sunday]. They were all upbeat," said Redknapp.
"They've got to realise they are in this position because they haven't really performed to their capabilities at the moment and they've got to do better.
"The players have to take responsibility for performances. They've got to up their performance level and get us out of trouble.
"I feel that there is enough ability here that with a bit of confidence we can hopefully climb the table."
Redknapp saved Portsmouth from relegation during two spells at the Fratton Park club, while also taking over at Tottenham when they were close to the bottom of the table and taking them to Champions League qualification the following season.
"We mustn't kid ourselves," he said. "This is much tougher than those two jobs in my opinion, but I'm optimistic we can pull it off.
"I want to be successful here, really badly. I want to keep this team in the Premier League.
Redknapp - QPR players must improve
"If the players try as hard as I am going to try we'll be successful."
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