Place the chicken breasts in the bottom of your slow cooker.
In a small bowl, mix together all the spices: chili powder, smoked paprika, cumin, garlic powder, onion powder, oregano, salt, and black pepper.
Sprinkle the spice mixture evenly over the chicken.
Pour in the chicken broth around the sides of the chicken (not directly on top so you don't rinse off the spices).
Cover and cook on low for 6–7 hours or high for 3–4 hours, until the chicken is tender and shreds easily.
About 45 minutes before it’s done, add the sliced bell peppers right on top of the chicken. Re-cover and let them cook until just tender.
Once done, shred the chicken directly in the slow cooker and stir everything to combine with the broth and peppers.
Sprinkle the shredded cheese on top, cover again, and let it melt for 5–10 minutes.
Serve warm in your favorite tortillas with any toppings you love.