The Brazil centre-back netted the 86th-minute equaliser that sent the match to extra time, before Thiago Silva cancelled out Eden Hazard's 96th-minute penalty to take the score to 3-3 on aggregate and send PSG - who saw Zlatan Ibrahimovic sent off controversially in the first half - through on away goals.
Luiz, who played for Chelsea from 2011 until 2014, did not hold back in celebrating the crucial header, but was quick to explain his reasons after full-time.
"My cycle finished in Chelsea, PSG gave me a great opportunity to continue my career," Luiz told Sky Sports. "I was very happy at Chelsea. I respect everyone.
"Tonight was good for me to score. I said I wouldn't celebrate but my emotions I couldn't control.
"Thank you to Chelsea and sorry I celebrated because I was so emotional.
"It is amazing for everyone, amazing for Paris club, for Paris city," he added. "We did a great game, we tried to win the game.
"I am happy to be in the next round but we have a long way to go to win the Champions League. We have to keep our feet on the floor."
