The Stamford Bridge team is likely to buy the former Arsenal striker for $ 29 million.
Chelsea are currently 12th in the Premier League. Tuchel beat Everton in the first round, but drew with Tottenham 2-2 and lost to Leeds 0-3 in the next two rounds.
The $29 million is the second offer Chelsea have made to Barca, after the initially rejected offer ($17 million). The Spanish side are likely to accept this week.
Coach Thomas Tuchel is in need of a suitable striker.
He managed Aubameyang for two years at Dortmund.
During that period, the Gabonese striker scored 79 goals in 95 matches. Aubameyang has also contributed 92 goals in 163 games for Arsenal and 13 goals in 24 games for Barca.
Chelsea no longer have a true centre-forward. This summer, they sold Timo Werner to RB Leipzig and let Romelu Lukaku return to Inter on loan. Meanwhile, 20-year-old rookie Armando Broja is out injured.
