Graham Potter has said the challenge of being Chelsea manager was "too big to turn down".
His first game in charge will be a home Champions League group game against Red Bull Salzburg on Wednesday.
"You have to look at the tradition, the quality, size and ambition of the club here," said Potter, who signed a five-year deal with the Blues.
"It's a completely different challenge from the one I had at Brighton.
"I had three fantastic years there, but I'm very thankful to the owners here for putting their trust in me."
He added: "My main job is to help the guys that are here, help them improve and put a team on the pitch that the supporters are proud of.
"We want to create our own team, our own identity so that it's recognisable. We'll fight every day for it."
Chelsea sacked Tuchel the day after defeat by Dinamo Zagreb in their opening Champions League group game, and face a Red Bull Salzburg side who drew with AC Milan in their first Group E match.
Potter has signed a five-year deal with ChelseaAsked if he had ever attended a Champions League match, Potter said: "Off the top of my head, I don't think I have - but it's a good time for me to get into the dugout.
"My experiences in the Champions League are just at supporter level.
"But obviously I've experienced the Europa League with Ostersund, winning at Galatasaray and getting through the group stage.
"Wherever we would start it would be a heck of an introduction, wherever we start it's going to be brilliant, so why not start here?"
Potter was appointed a day after the departure of Tuchel and on the same day as the death of Queen Elizabeth II was announced.
Football paused last weekend as a mark of respect following the Queen's death, meaning Chelsea's match against Fulham was postponed.
The home game against Red Bull Salzburg is taking place, but the Premier League match against Liverpool on Sunday has also been called off "due to events surrounding the Queen's funeral" on Monday, 19 September.
The international break comes after this weekend's games, meaning Potter's first top-flight match will be at Crystal Palace on Saturday, 1 October.
"We quickly had to make a decision," said Potter about his appointment. "There were a lot of talks and it was very intense.
"I got a nice feeling for the owners on a human level. They are good people. Very intelligent people with an understanding of what they want to achieve.
"They've thought in the long term, they have a plan so that was exciting.
"The challenge was too big to turn down. It felt right for me.
"I'll always be respectful and thankful for Brighton & Hove Albion, but this is an amazing football club and an amazing challenge for us."
Boehly on Tuchel and Chelsea plans
Meanwhile, Chelsea chairman Todd Boehly says he is considering a multi-club model as a way to develop young players.
The new co-owner cited Manchester City, who own several teams worldwide and the Red Bull teams at Leipzig and Salzburg, as successful models.
Speaking at the SALT conference in New York, Boehly spoke about sacked manager Thomas Tuchel for the first time, saying the German didn't have "a shared vision for the future".
"We have talked about having a multi-club model, I would love to continue to build out the footprint," Boehly said.
"One of the challenges at Chelsea is that when you have 18, 19, 20-year old superstars, you loan them to other clubs but you put their development in someone else's hands.
"I think our goal is to make sure that we can show pathways to young superstars to get on the Chelsea pitch while getting them real game time. And to me the way to do that is through another club somewhere in a really competitive league in Europe."
