A lot of behavioral finance research is done in econ departments, some of which have programs/groups/centers focusing on it. There are also people studying it in business school finance departments, but they seem a little less organized.
This might be a case where it makes sense to apply to econ programs in addition to finance.
Here’s a survey of research areas in behavioral finance: Noahpinion: Behavioral economics vs. behavioral finance
Here’s a ranking of behavioral econ programs. Take it with a grain of salt. Economics Field Rankings: Cognitive & Behavioural Economics | IDEAS/RePEc
Here is a list of some econ programs that specialize in this area. The Big List of Behavioral Finance and Behavioral Economics Degrees — Nocturne Capital
Lacking a top down ranking of behavioral finance programs, I would suggest you should look at it from a bottom up perspective. Do a Google Scholar search on research topics you are interested in and see which authors pop up. Look at schools you are interested in and see whether they have faculty doing behavioral work.