Unai Emery insists Paris Saint-Germain are still searching for an identity, despite scoring five goals without reply against Celtic in their opening Champions League fixture.

Big-spending French giants PSG kicked off their Group B campaign with an impressive 5-0 away rout of Celtic, the expensive front three of Edinson Cavani, Kylian Mbappe and Neymar all finding the net in a rampant first-half display.

PSG's handsome victory on Tuesday maintains their 100 per cent winning record this season, yet Emery believes there is still plenty of work to do.

"The club wants to learn from things that have happened. We've worked to improve things in the team, together," he told the media.

"The team has made a great effort in the transfer market to improve and grow, but it's more about work. Today, we're content, but we have to be tranquil, be confident and continue.

"But a match like tonight is good for the confidence. We're searching a clear identity. And this is a good step forward to prepare for more difficult times."

Cavani converted a 40th-minute penalty to become PSG's all-time leading scorer in European competitions, a record he previously shared with former team-mate Zlatan Ibrahimovic.

The Uruguayan grabbed another in the second half, acrobatically heading home a cross from the left, while the hosts also helped their opponents with an own goal from defender Mikael Lustig.

Emery was particularly pleased with the way his players dictated the tempo right from the kick-off, and singled out midfielder Adrien Rabiot, who set up Neymar's 19th-minute opener before being withdrawn in the second half, for special praise.

"The strength of the team was many things. We controlled everything all across the park, from the defence to the attack," the Spaniard said. 

"But it's true, the midfield showed their control of the ball and the match, with the ball and without the ball. It was a team effort. We made great work at the start of the match.

"The progression of Rabiot is impressive. He can improve things, but the match was good for him."