Season the chicken breasts with salt and pepper on both sides.
Sear the chicken breasts in a skillet over medium-high heat with olive oil. Let each side cook for about 2-3 minutes, until it has a crust.
In a medium bowl, combine the barbecue sauce, soy sauce, brown sugar, minced garlic, grated ginger, and the pineapple juice from the can. Stir until the sauce is evenly combined.
Place the seasoned chicken breasts in the bottom of the slow cooker.
Add the chopped bell peppers on top of the chicken.
Pour the sauce over the chicken and vegetables so that it covers everything evenly.
Place the cover on the slow cooker and cook on low for 6-7 hours or on high for 3-4 hours. The chicken should be very tender and cooked through.
When there is about 30 minutes left, add the cornstarch slurry to the sauce and stir in. Add the pineapple chunks and cover and cook for 30 more minutes.
Serve the Hawaiian Chicken over cooked white or brown rice. Garnish with sliced green onions and sesame seeds.