Stir together the first nine ingredients in the slow cooker. Add the chicken and turn it over a few times so that it's well coated. Put the sweet potato, onion, and peppers on top of the chicken.
Cover and cook for 4 to 6 hours on high or 7 to 9 hours on low.
Stir the mango, cashews, and lime juice into the curry, then cover and heat just until the mango is no longer frozen (about 20 minutes).
Serve the curry with cilantro.