Is it possible to change the application area of research while looking for a postdoc position after PhD?
For whatever it’s worth, I changed my field between PhD and postdocs as well.
In my case, my main goal was to find a thriving field (where I could make some use of my skills and that would match my general interests).
My general rationale was this:
Most fields produce enough qualified and willing PhD graduates to fill their postdoc needs, against which I wouldn’t stand a chance.
The only exception to this is a strongly expanding field.
Hence I just applied to interesting positions and concluded that if I would get a position the respective field would be sufficiently thriving.
(And indeed many other people in my current field came from other fields.)

As you appear to have a specific target field in mind, it may also help to get insights from professors in that field as to how saturated the postdoc job market is.
If you are up against an army of competitors with more experience, seeking jobs here may be a waste of time.
If on the other hand, your main goal is to leave your current field, you can hedge your bets by being open about potential target fields.

Now, there are some exceptions, alternatives, and caveats to consider:


Sometimes, a postdoc is hired with the explicit goal of transferring or applying knowledge from another field.
However, in this case, the job ad will state corresponding requirements.
Whether saturated or not, postdoc job markets are only feature a small number of candidates and positions, and thus they are strong subject to statistical fluctuations.
It may thus easily happen that a professor cannot fill a postdoc position even in a stagnating field, and settles for somebody less qualified than they hope for.
(On the other hand, you are still in a stagnating field then.)
It is possible that a vacancy remains unfilled due to the professor being known to be scientifically or socially incompetent in the field.
So, watch out for red flags.


So, I would suggest to just apply to positions that interest you (if only to get application routine).
I would be upfront about the fact that you are changing fields, and focus on your enthusiasm for the target field and general scientific skills, in particular anything that demonstrates that you can adapt to a new topic and are good at scientific work in general – which after all is at least half of what a good PhD should be about.
Getting a job while lacking a required experience is a disaster waiting to happen.