In a large skillet over medium-high heat, saute chicken, onion, pepper, and garlic in oil until chicken is cooked through and veggies are tender. Stir in tomato paste and transfer mixture to a 3-qt crockpot. Add tomatoes, black beans, tomato sauce, chipotle, chicken broth, chili powder, cumin, and salt and pepper to taste to crockpot and stir to combine.