The Premier League club advanced 5-1 on aggregate over their Swedish opponents who had reached the last four of a European competition for the first time.
In the decider, which takes place on May 28 in Wroclaw, Poland, Chelsea will meet Real Betis after the Spanish club drew 2-2 after extra time with Fiorentina in Italy for a 4-3 aggregate win.
At Stamford Bridge on Thursday night, Kiernan Dewsbury-Hall collected a through pass from Tyrique George before scoring the winner with a low left-footed shot in the 38th minute.
Chelsea remain on course to become the first club to win all major European competitions.
The Blues have claimed the Champions League (2012, 2021), Europa League (2013, 2019), Cup Winners' Cup (1971, 1998) and Super Cup (1998, 2021).
Chelsea manager Enzo Maresca used only Marc Cucurella from the team that beat the new Premier League champion Liverpool 3-1 on Sunday.
Sixteen-year-old midfielder Reggie Walsh was given his first career start and made his presence felt, drawing frequent fouls from the opposition defence. When he was used as substitute in the first leg, he became the third youngest player for Chelsea, the club said.
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